Phillip W Taylor

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Abstract: Diet has a profound influence on the fitness of adult tephritid flies. Mass-reared flies are provided yeast hydrolysate as a rich source of nutrition that supports rapid sexual development and mating success. In contrast, wild tephritid flies often live in environments where food may be hard to find, and these are the conditions that sexually immature mass-reared sterile males encounter when released into the field during sterile insect technique campaigns. The effect of natural food sources (bat guano, bird droppings, citrus pollen, and wheat pollen) on the sexual development of adult mass-reared fertile, mass-reared sterile, and wild male Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), was determined by measuring ejaculatory apodeme size. Inclusion of yeast hydrolysate in the adult diet was associated with faster growth of the ejaculatory apodeme in comparison with all other diets. Effects of diet were far less pronounced in mass-reared males, which may indicate reduced nutritional requirements, whereas the ejaculatory apodeme of wild males fed on natural sources of food or sucrose alone did not increase in size over the first 20 days of adult life.

Abstract: Assassin bugs (Stenolemus bituberus) hunt web-building spiders by invading the web and plucking the silk to generate vibrations that lure the resident spider into striking range. To test whether vibrations generated by bugs aggressively mimic the vibrations generated by insect prey, we compared the responses of spiders to bugs with how they responded to prey, cour ting male spiders and leaves falling into the web. We also analysed the associated vibrations. Similar spider orientation and approach behaviours were observed in response to vibrations from bugs and prey, whereas different behaviours were observed in response to vibrations from male spiders and leaves. Peak frequency and duration of vibrations generated by bugs were similar to those generated by prey and cour ting males. Further, vibrations from bugs had a temporal structure and amplitude that were similar to vibrations generated by leg and body movements of prey and distinctly different to vibrations from courting males or leaves, or prey beating their wings. To be an effective predator, bugs do not need to mimic the full range of prey vibrations. Instead bugs are general mimics of a subset of prey vibrations that fall within the range of vibrations classi�ed by spiders as �prey�.

Abstract: Pupae of the Queensland fruit fly or Q-fly Bactrocera tryoni (Froggatt) are irradiated routinely to induce reproductive sterility in adults for use in sterile insect technique programmes. Previous studies suggest that adult sexual performance and survival under nutritional and crowding stress are compromised by the current target dose of radiation for sterilization (70�75 Gy), and that improved mating propensity and survival under stress by irradiated males may be achieved by reducing the target sterilization dose without reducing the level of induced sterility. This raises the question of the amount by which the irradiation dose can be reduced before residual fertility becomes unacceptable. The present study measures the levels of residual fertility in male and female irradiated Q-flies at different irradiation doses (20, 30, 40, 50, 60 and 70 Gy), and investigates the possibility that fecundity and fertility increase between 10�15 and 30�35 days post emergence. Male flies require a higher dose than females to induce sterility, with no residual fertility found in females irradiated at doses of 50 Gy or above, and no residual fertility found in males irradiated at doses of 60 Gy or above. Irradiated females are more fecund at 30�35 days post emergence than at 10�15 days. However, fertility does not increase between 10 and 15 days post emergence and 30�35 days, even at doses below 50 Gy. The present study shows that there is scope to reduce the target sterilization dose for Q-flies below that of the current dose range (70�75 Gy) at the same time as retaining an adequate safety margin above radiation doses at which residual fertility can be expected.

Abstract: The distribution, systematics and ecology of Bactrocera tryoni, the Queensland fruit fly, are reviewed. Bactrocera tryoni is a member of the B. tryoni complex of species, which currently includes four named species, viz. B. tryoni ssp., B. neohumeralis, B. melas and B. aquilonis. The species status of B. melas and B. aquilonis is unclear (they may be junior synonyms of B. tryoni) and their validity, or otherwise, needs to be confirmed as a matter of urgency. While Queensland fruit fly is regarded as a tropical species, it cannot be assumed that its distribution will spread further south under climate change scenarios. Increasing aridity and hot dry summers, as well as more complex, indirect interactions resulting from elevated CO2, make predicting the future distribution and abundance of B. tryoni difficult. The ecology of B. tryoni is reviewed with respect to current control approaches (with the exception of sterile insect technique (SIT) which is covered in a companion paper). We conclude that there are major gaps in the knowledge required to implement most noninsecticide-based management approaches. Priority areas for future research include host�plant interactions, protein and cue-lure foraging and use, spatial dynamics, development of new monitoring tools, investigating the use of natural enemies and better integration of fruit flies into general horticultural IPM systems.

Abstract: 1. Spiders are the most sexually size dimorphic terrestrial animals and the evolution of this dimorphism is controversial. Patterns of sexual size dimorphism (SSD) in spiders have been related to individual performance and size. In 2002 Moya-Laraño, Halaj & Wise proposed the �gravity hypothesis� to explain patterns of sexual size dimorphism in spiders whereby species building webs high in the vegetation are predicted to show greater SSD than those that built lower down. They advocated an advantage in climbing speed in smaller males searching for females in high places. The gravity hypothesis predicts a negative relationship between male size and climbing speed. In 2007 Brandt & Andrade questioned this interpretation and proposed that the pattern of SSD in spiders is better explained by an advantage for larger males of low-dwelling species to run faster along the ground. This model also requires selection for potandry in males to generate SSD. 2. We induced male spiders to run a standard distance up vertical poles of different diameters to examine the predicted relationship between size and climbing speed. We tested two species of extremely size-dimorphic orb-web spiders, Argiope keyserlingi and Nephila plumipes, that differ in the height at which females tend to build webs, and one species of cursorial foraging jumping spider, Jacksonoides queenslandica, with low levels of size dimorphism. We also examined morphological determinants of horizontal motility by inducing males to run along a raceway. 3. Substrate diameter was consistently found to influence climbing performance. In N. plumipes, climbing speed was slowest on the widest diameter substrate. In A. keyserlingi, residual leg length and substrate diameter interacted to determine climbing speed, while in J. queenslandica, there was an interaction between body size and substrate diameter on climbing speed. In the effect of substrate diameter, we have identified a potential bias in previous tests of this hypothesis related to methodology. 4. Our results do not support the prediction of the gravity hypothesis. There was no evidence of a negative relationship between body size and climbing speed in the two orb-web species with high levels of SSD. Our results are also not consistent with the update of the gravity hypothesis that suggests a curvilinear relationship between climbing speed and size. 5. Body size was positively associated with maximum running speed only in the cursorial hunter J. queenslandica. For this spider, results are more consistent with Brandt & Andrade�s (2007a) explanation for variation in SSD in spiders, that larger males are selected for superior running ability in low-dwelling species, rather than selection for smaller size for climbing to females in high-dwelling species (Moya-Laraño et al. 2002). However, evidence of selection for protandry in males envisioned in this model is still lacking.

Abstract: Desiccation resistance is important for the survival of adult insects but this key physiological trait has rarely been studied in tephritid flies. In the present study, desiccation resistance of female and male adult Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) is determined with respect to age after adult eclosion. Resistance to acute starvation is measured over the same period to disentangle the competing roles of water loss and food deprivation. Survival of adult B. tryoni subjected to conditions of low humidity and starvation is reduced considerably in comparison with adults that are subjected to starvation alone. Desiccation resistance of adult female B. tryoni was generally lower than that of adult males. Desiccation resistance of adult B. tryoni declines in a continuous and regular manner over the first 20 days after adult eclosion. The regular pattern of declining resistance to desiccation with age in B. tryoni indicates that this reduction is not associated with the onset of maturity and maintenance of reproductive structures, or with sexual activity. In contrast, resistance to starvation was similar at 0 and 6 six days after adult eclosion, and declines thereafter. Survival under starvation and water stress is not related to wing length, a standard measure of fly size.

Abstract: Background Locomotor performance in ecologically relevant activities is often linked to individual fitness. Recent controversy over evolution of extreme sexual size dimorphism (SSD) in spiders centres on the relationship between size and locomotor capacity in males. Advantages for large males running over horizontal surfaces and small males climbing vertically have been proposed. Models have implicitly treated running and climbing as functionally distinct activities and failed to consider the possibility that they reflect common underlying capacities. Findings We examine the relationship between maximum climbing and running performance in males of three spider species. Maximum running and climbing speeds were positively related in two orb-web spiders with high SSD (Argiope keyserlingi and Nephila plumipes), indicating that for these species assays of running and climbing largely reveal the same underlying capacities. Running and climbing speeds were not related in a jumping spider with low SSD (Jacksonoides queenslandica). We found no evidence of a performance trade-off between these activities. Conclusions In the web-spiders A. keyserlingi and N. plumipes good runners were also good climbers. This indicates that climbing and running largely represent a single locomotor performance characteristic in these spiders, but this was not the case for the jumping spider J. queenslandica. There was no evidence of a trade-off between maximum running and climbing speeds in these spiders. We highlight the need to establish the relationship between apparently disparate locomotor activities when testing alternative hypotheses that yield predictions about different locomotor activities. Analysis of slopes suggests greater potential for an evolutionary response on performance in the horizontal compared to vertical context in these spiders.

Abstract: Assassin bugs from the genus Stenolemus (Heteroptera, Reduviidae) are predators of web-building spiders. However, despite their fascinating lifestyle, little is known about how these insects hunt and catch their dangerous prey. Here we characterise in detail the behaviour adopted by S. bituberus (Stål) during encounters with web-building spiders, this being an important step toward understanding this species� predatory strategy. These bugs employed two distinct predatory tactics, �stalking� and �luring�. When stalking their prey, bugs slowly approached the prey spider until within striking range, severing and stretching threads of silk that were in the way. When luring their prey, bugs attracted the resident spider by plucking and stretching the silk with their legs, generating vibrations in the web. Spiders approached the luring bug and were attacked when within range. The luring tactic of S. bituberus appears to exploit the tendency of spiders to approach the source of vibrations in the web, such as might be generated by struggling prey.

Abstract: Copula duration and sperm storage patterns can directly or indirectly affect �tness of male and female insects. Although both sexes have an interest in the outcome, research has tended to focus on males. To investigate female in�uences, we compared copula duration and sperm storage of Queensland fruit �y females that were intact, or had been incapacitated through decapitation or abdomen isolation. We found that copulations were far longer when females had been incapacitated, indicating that constraints imposed on copula duration by intact females had been relaxed. Repeatability of copula duration for males was very low regardless of female treatment, and this is also consistent with strong female in�uence. Number of sperm in the spermathecae was not in�uenced by female treatment, suggesting that female abdominal ganglia control the transport of sperm to these long-term storage organs. However, more sperm were found in the ventral receptacles of incapacitated females compared to intact females. Overall, results implicate cephalic ganglia in regulation of copula duration and short-term sperm storage in the ventral receptacle and abdominal ganglia in regulation of long-term sperm storage in the spermathecae.

Abstract: Mass-reared sterile tephritid flies released in sterile insect technique (SIT) programmes exhibit behaviours, physiology and longevity that often differ from their wild counterparts. In the present study, video recordings of flies in laboratory cages are used to determine whether the sequential processes of mass-rearing and sterilization (using gamma radiation) that are integral to SIT affect general activity patterns of male and female Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) (�Q-flies�). When compared with wild flies, mass-reared flies exhibit a marked reduction in overall activity, and further reduction is found following sterilization. In terms of frequency of activities, both fertile and sterile mass-reared Q-flies fly less often and exhibit more bouts of inactivity and grooming than wild Q-flies. In addition, in terms of duration of activities, fertile and sterile mass-reared Q-flies spend less time flying and more time walking, grooming and inactive than wild Q-flies. While fertile and sterile mass-reared flies are similar in other regards, sterile mass-reared flies spend more time inactive than fertile mass-reared flies. These findings raise new questions about how changes in behaviour and activity levels may influence the performance of mass-reared sterile Q-flies in the field, and of the physiological and metabolic processes that are involved. The frequency and duration of inactivity could provide a simple but powerful and biologically relevant test for quality in mass-rearing and SIT programs.

Abstract: Technical note - no abstract

Abstract: The present study is an important step toward calibrating, validating and improving irradiation methods used for Queensland fruit fly sterile insect technique (SIT). We used routine IAEA/USDA/FAO quality control tests assessing percentage emergence, flight ability, sex ratio, mortality under stress, longevity under nutritional stress, reproductive sterility and sexual competitiveness, to assess the impact of a range of target irradiation doses (60, 65, 70, 75 and 80 Gy) on the product quality of mass reared Queensland fruit fly used in SIT. Sterility induction remained adequate (> 99.5%) across the full range of irradiation doses tested. However there was significant reduction in survivability and competitiveness of irradiated flies as dose increased. The current target sterilizing dose for SIT of 70-75 Gy is associated with elevated damage to flies. Our data suggest that adequate sterility and improved fly quality could be achieved through a small reduction in target sterilizing dose.

Abstract: Caloric restriction (CR) has been widely accepted as a mechanism explaining increased lifespan (LS) in organisms subjected to dietary restriction (DR), but recent studies investigating the role of nutrients have challenged the role of CR in extending longevity. Fuelling this debate is the difficulty in experimentally disentangling CR and nutrient effects due to compensatory feeding (CF) behaviour. We quantified CF by measuring the volume of solution imbibed and determined how calories and nutrients influenced LS and fecundity in unmated females of the Queensland fruit fly, Bactocera tryoni (Diptera: Tephritidae). We restricted flies to one of 28 diets varying in carbohydrate:protein (C:P) ratios and concentrations. On imbalanced diets, flies overcame dietary dilutions, consuming similar caloric intakes for most dilutions. The response surface for LS revealed that increasing C:P ratio while keeping calories constant extended LS, with the maximum LS along C:P ratio of 21:1. In general, LS was reduced as caloric intake decreased. Lifetime egg production was maximized at a C:P ratio of 3:1. When given a choice of separate sucrose and yeast solutions, each at one of five concentrations (yielding 25 choice treatments), flies regulated their nutrient intake to match C:P ratio of 3:1. Our results (i) demonstrate that CF can overcome dietary dilutions; (ii) reveal difficulties with methods presenting fixed amounts of liquid diet; (iii) illustrate the need to measure intake to account for CF in DR studies and (iv) highlight nutrients rather than CR as a dominant influence on LS.

Abstract: Ultrastructure of male reproductive accessory glands and ejaculatory duct in the Queensland fruit fly (Q-fly), Bactrocera tryoni, were investigated and compared with those of other tephritid flies. Male accessory glands were found to comprise one pair of mesodermic glands and three pairs of ectodermic glands. The mesodermic accessory glands consist of muscle-lined, binucleate epithelial cells, which are highly microvillated and extrude electron-dense secretions by means of macroapocrine transport into a central lumen. The ectodermic accessory glands consist of muscle-lined epithelial cells which have wide subcuticular cavities, lined with microvilli. The electron-transparent secretions from these glands are first extruded into the cavities and then forced out through small pores of the cuticle into the gland lumen. Secretions from the two types of accessory glands then flow into the ejaculatory duct, which is highly muscular, with epithelial cells rich in rough endoplasmic reticulum and lined with a thick, deeply invaginated cuticle. While there are some notable differences, reproductive accessory glands of male Q-flies generally resemble those of the olive fruitfly, Bactrocera oleae, and to a lesser extent the Mediterranean fruit fly, Ceratitis capitata.

Abstract: Recent laboratory studies of mass-reared flies in small cages have found that periods of just 24- or 48-h access to yeast hydrolysate can substantially enhance mating performance of mass-reared male Queensland fruit flies, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) (�Q-flies�). Using field cage tests that provide a better approximation of nature, we here investigated whether access to yeast hydrolysate for 48 h after adult emergence improves the ability of male and female mass-reared, sterile Q-flies to compete sexually with wild-type flies that had been provided continuous access to yeast hydrolysate. Mating probability of sterile males was significantly increased by 48-h access to yeast hydrolysate; sterile males provided 48-h access to yeast hydrolysate had mating probability similar to that of wild males provided continuous access to yeast hydrolysate, whereas sterile males deprived of access to yeast hydrolysate had much lower mating probability. Unlike males, access to yeast hydrolysate for 48 h did not increase mating probability of sterile female Q-flies. We instead found that wild females provided continuous access to yeast hydrolysate had higher mating probability than sterile females that did or did not have 48-h access to yeast hydrolysate. This result raises the possibility that a bisexual Q-fly strain might operate essentially as a male-only release when the flies are given access to yeast hydrolysate during a 48-h pre-release holding period. Sterile males given access to yeast hydrolysate for 48 h mated significantly earlier in the evening than wild males and, as in other recent studies, this tendency was associated with an increased tendency to mate on the trees rather than the cage walls. There was no evidence of sexual isolation in this study, as wild and sterile mass-reared flies showed no evidence of preferential mating with their own kind. Further studies are now needed to assess the potential for pre-release access to yeast hydrolysate to improve sexual performance and longevity of sterile, mass-reared, Q-flies in the field.

Abstract: 1. Animals, as they move through their environment, leave traces of their passage that can be informative to others and convey significant advantages to the animal producing them. However, such traces may also reveal presence, location or identity to enemies. 2. We studied an araneophagic (�spider-eating�) assassin bug, Stenolemus bituberus (Heteroptera, Reduviidae), testing whether it associated with areas containing chemotactile traces (e.g. draglines, excreta) left behind by nine sympatric spider species. Stenolemus bituberus were presented with a choice between a substrate containing draglines and a clean substrate. Each hour, for a duration of 12 h, we recorded which substrate was occupied. 3. Stenolemus bituberus tended to associate especially with draglines left by spiders from the genus Achaearanea, their most common prey in nature. 4. These results suggest that S. bituberus exploits draglines from these spiders as cues for indicating prey presence. We also found an increasing tendency to associate with draglines from some spider species through the day, which may be related to circadian patterns or slower response times of some individuals.

Abstract: Males of many species perform elaborate displays in which multiple ornaments feature prominently. However, female preferences often depend upon both display movements and a subset of the ornaments. This response selectivity means that female choice cannot explain the function of non-preferred ornaments. These structures may instead have an ancillary function, e.g. enhancing signal efficacy or modifying information content. Male jungle fowl possess multiple ornaments (comb and wattles), which feature prominently during food-related displays (tidbitting). There is strong evidence for female choice based on display frequency and comb characteristics, but little evidence for choice based on wattles. Wattles are thin, elastic structures that hang loosely from a male's lower mandibles and vary in size over a male's lifetime. These structures swing rapidly during tidbitting, potentially increasing the area around the head and increasing image motion. Males also tidbit more vigorously with highly preferred food, increasing wattle displacement and thereby potentially affecting information content. We tested the prediction that wattles enhance signal efficacy and information content by conducting high-definition playbacks, using 3D animations of tidbitting males with differing wattle properties. Results revealed that the food searching response of receivers was robust to changes in wattle size and motion. Increased wattle displacement did not decrease orienting latency or increase food-searching duration, which suggests that wattles do not contribute significantly to information content. However, apparent wattle size significantly decreased orienting latency, demonstrating that wattles increase the conspicuousness of the tidbitting signal. These results suggest that wattles are maintained because they enhance signal efficacy.

Abstract: Male insects that are unable to replenish sperm supplies between matings can suffer fitness costs either because their mates are more likely to accept subsequent suitors, or because their sperm are outnumbered when females do remate. We assessed the ability of fertile and sterile (irradiated) male Queensland fruit flies, Bactrocera tryoni (�Q-flies�), to have sperm stored by five sequential mates as well as the association between sperm depletion and female remating tendency. Sequential mates of fertile males stored similar numbers of sperm, indicating ample ability to replenish and maintain constant supplies between their once-daily mating opportunities. In contrast, sequential mates of sterile males stored progressively fewer sperm, with only trivial numbers of sperm stored by females mated by sterile males that had mated with two or more females previously. Despite the massive reduction in sperm storage by sequential mates of sterile males, fertile and sterile males were similar in their ability to induce sexual inhibition in their mates (to at least 30 days) and neither showed any decline in this ability across sequential matings. The ability of multiple-mated sterile males to induce sexual inhibition in their mates despite near or complete absence of sperm provides compelling evidence that sperm abundance plays no role in the induction of sexual inhibition in this species.

Abstract: Male wolf spiders (Lycosidae) in the genus Schizocosa vary in use of seismic and visual components of courtship display, ranging from unimodal (seismic only) to multimodal (seismic and visual). Studies show that variation in individual modes influences female receptivity, but responses to isolated signals may not be equivalent. To examine redundancy and interaction between modes, we compared female responses to isolated and combined courtship signals from males of two sympatric sibling species that differ in use of visual and seismic modes, S. ocreata and S. rovneri. Females of both species detected multimodal stimuli faster than visual or seismic cues alone, but they differed in responses to cues once they oriented. Female S. ocreata approached males performing isolated visual and seismic cues with equal frequency, but approached males performing multimodal cues more often. A greater proportion of female S. ocreata responded more receptively to multimodal cues than to seismic or visual cues alone, and showed higher rates of receptivity displays with multimodal cues. In contrast, female S. rovneri showed no differences in approaches, but responded more often and with higher display rates to seismic cues alone or multimodal cues, but not visual cues. These results suggest multimodal signalling increases detection of males by females, but that use of signal modes varies between even closely related sibling species. For S. rovneri, male signals in different modes are nonredundant, with seismic cues dominant over visual cues when presented alone or in multimodal signals. In contrast, for S. ocreata, male signals in different modes are redundant (eliciting the same responses from females with similar frequency), while the greatly increased responsiveness to multimodal signals indicates multiplicative enhancement.

Abstract: Predators of dangerous prey risk being injured or killed in counter-attacks and hence may use risk-reducing predatory tactics. Spiders are often dangerous predators to insects, but for a few, including Stenolemus bituberus assassin bugs, web-building spiders are prey. Despite the dangers of counter-attack when hunting spiders, there has been surprisingly little investigation of the predatory tactics used by araneophagic (spider-eating) insects. Here, we compare the pursuit tendency, outcome and predatory tactics of S. bituberus against five species of web-building spider. We found that S. bituberus were most likely to hunt and capture spiders from the genus Achaearanea, a particularly common prey in nature. Capture of Achaearanea sp. was more likely if the prey spider was relatively small, or if S. bituberus was in poor condition. S. bituberus used two distinct predatory tactics, �stalking�, in which they slowly approached the prey, and �luring�, in which they attracted spiders by manipulating the web to generate vibrations. Tactics were tailored to the prey species, with luring used more often against spiders from the genus Achaearanea, and stalking used more often against Pholcus phalangioides. The choice of hunting tactic used by S. bituberus may reduce the risk posed by the prey spider.

Abstract: Autotomy is a taxonomically widespread antipredator tactic that allows animals to escape life-threatening situations. Opposing the benefits of survival, animals that have autotomized appendages may later suffer reduced ability in important determinants of fitness. Male Schizocosa ocreata wolf spiders use their forelegs during courtship for visual displays, for tactile courtship, and to defend against attacks by females. In nature they are often found missing one, and sometimes both, forelegs. We found that autotomy of one foreleg has little effect on male ability to mate with virgin females, but that autotomy of both forelegs causes a significant reduction in mating success. Among males that mated, autotomy of one or both forelegs did not influence latency until mating, period spent mounted, probability that his mate would accept a subsequent suitor, or probability that his mate would kill a subsequent suitor.

Abstract: The mating performance �eld cage test is a required periodic quality-control assessment for factory- reared fruit �ies used for the sterile insect technique. The FAO/IAEA/USDA guidelines for assessing fly quality state that if during tests a large proportion of flies call and mate on cage walls, away from host trees, then environmental conditions within the cage need to be adjusted and tests repeated. Here we test effects of cage design, specifcally mesh colour (green, white) and addition of supplementary shade, on the mating behaviour of Queensland fruit fly (Q-fly), Bactrocera tryoni Froggatt (Diptera: Tephritidae). Observations were made over a 4-h period at dusk when these flies mate. Changes in environmental conditions in each cage over the dusk period varied with cage design. We recorded the highest proportion of matings taking place on trees as opposed to cage walls (> 90%) in the unshaded white cage, the shaded white and un-shaded green cages being intermediate (ca. 70%), and the shaded green cage had the least (ca. 40%). The effects of field cage colour and supplementary shade on mating behaviour are discussed. We recommend that Q-fly field cage tests should be conducted in cages with a light coloured mesh, and that supplementary shading should only be applied if there is a need to adjust temperature and light within the cage.

Abstract: Behavior and sounds associated with mating of mass-reared irradiated and untreated (nonirradiated) Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) males were analyzed from synchronous acoustic and video records. The flies tested were from a population used in sterile release programs that help maintain fruit-fly-free areas in Australia. Males typically produce �calling,� �courtship,� and �copula� sounds as mating progresses. Calling sounds are variable-duration bursts of wing vibrations produced before the male orients toward the female. Rapid bursts of courtship sounds of relatively constant duration are produced after orientation toward the female. Copula sounds of variable amplitude and duration are produced after mounting. There was a significant negative correlation between courtship wingbeat frequency and wing width of untreated males, and those that copulated had a lower frequency than those that failed. Wingbeat frequencies in flight, calling, courtship, and copula sounds were significantly correlated within flies, possibly because they all are produced by the same flight motor, with amplitudes affected by the positioning of the wings relative to �stops� on the thorax. The temporal patterns of calling and courtship sounds differed significantly between irradiated and untreated males. Irradiation is known to damage insect central nervous system interneurons and thereby alter the coordination and timing of behavioral activities, but this is the first study identifying an effect of irradiation on tephritid calling and courtship sounds. Although differences in temporal patterns of calling and courtship sounds have potential to affect mating competitiveness, no differences were observed in proportions of irradiated and untreated males that copulated in the laboratory.

Abstract: Queensland fruit fly (Bactrocera tryoni; Q-fly) pupae are routinely irradiated to induce reproductive sterility in adults released in a sterile insect technique programme. Although there have been some studies of how total dose influences fly quality, dose rate has not been considered. In the present study, pupae were irradiated at a target dose range of 70�75 Gy at dose rates of approximately 5, 7, 26, 57 and 80 Gy/min and were then subjected to routine IAEA/FAO/USDA quality control tests including emergence, flight ability, mortality under stress and sterility induction. No significant effects of dose rate were found on emergence or flight ability. Sterility induction was also found to be independent of dose rate, a result conforming to a �one-hit� ionizing event hypothesis. Flies irradiated at higher dose rates suffered increased mortality under stress. This appears to stem from an increased tendency to over-shoot the target dose when irradiating at high dose rates. We recommend that, to reduce potential error in total target dose, the lowest practical dose rate be used when irradiating Q-fly pupae for use in the sterile insect technique.

Abstract: Mating success of male insects is commonly determined by their ability to find and copulate with multiple females, but is also determined by their ability to transfer an effective ejaculate. In order to succeed in these tasks, males must first succeed in replenishing the necessary reproductive reserves between mating opportunities. We here investigate the ability of male Queensland fruit flies ('Q-fly') to recover from their first matings in time to both mate again the following day and to induce sexual inhibition in successive mates. We have previously found that accessory gland fluids (AGFs) transferred in the ejaculate of male Q-flies are directly responsible for induction of sexual inhibition in their mates. We here investigate changes in male accessory gland, testis and ejaculatory apodeme dimensions that are likely to reflect depletion and recovery of contents. We found no differences between virgin and previously mated males in their ability to obtain matings or to induce sexual inhibition in their mates, indicating a full recovery of the necessary reproductive reserves between mating opportunities. Whereas no changes were detected in testis or ejaculatory apodeme size following mating, the recovery of male ability to inhibit female remating was closely reflected in the mesodermal accessory gland dimensions; these accessory glands greatly diminished in size (length and area) immediately after mating, with recovery commencing between 5.5 and 11 h after mating. The accessory glands then expanded to reach their original size in time to mate the following day and induce sexual inhibition in the next mate.

Abstract: Modest dietary restriction (DR) prolongs life in a wide range of organisms, spanning single-celled yeast to mammals. Here, we report the use of recent techniques in nutrition research to quantify the detailed relationship between diet, nutrient intake, lifespan, and reproduction in Drosophila melanogaster. Caloric restriction (CR) was not responsible for extending lifespan in our experimental flies. Response surfaces for lifespan and fecundity were maximized at different protein-carbohydrate intakes, with longevity highest at a protein-to-carbohydrate ratio of 1:16 and egg-laying rate maximized at 1:2. Lifetime egg production, the measure closest to fitness, was maximized at an intermediate P:C ratio of 1:4. Flies offered a choice of complementary foods regulated intake to maximize lifetime egg production. The results indicate a role for both direct costs of reproduction and other deleterious consequences of ingesting high levels of protein. We unite a body of apparently conflicting work within a common framework and provide a platform for studying aging in all organisms.

Abstract: 1 Recent studies have shown that continuous access to a protein source (yeast hydrolysate) can greatly enhance the sexual performance of male Queensland fruit flies (Bactrocera tryoni ; �Q-flies�). However, in Sterile Insect Technique programmes used to eradicate or suppress wild populations, mass-reared Q-flies are typically fed only sucrose and water for up to 2 days before release. 2 We investigated whether adding a protein source to the diet of male Q-flies for a 24- or 48-h window after emergence and then removing it is sufficient to enhance mating probability, latency to mate, copula duration, probability of sperm storage, number of sperm stored, female remating tendency and longevity of male Q-flies. 3 Protein-fed males were more likely to mate than males fed only sucrose, especially when young. Protein-fed males also had shorter mating latencies and longer copulations than protein-deprived males. 4 Females mated by protein-fed males were more likely to store sperm, stored more sperm and were less likely to remate than were females mated by protein deprived males. Females were also less likely to remate if their first mate had been large. 5 Overall, providing male Q-flies access to a protein source for a 24- or 48-h window early on in their adult life was sufficient to greatly enhance all assessed measures of performance. Although 24-h access was sufficient for a notable enhancement, further benefits were evident in males provided 48-h access. 6 The results are discussed in terms of the practical implications for Sterile Insect Technique programs used to eradicate or suppress wild Q-fly populations.

Abstract: Nutrition is commonly a powerful determinant of sexual performance in insects, and recent studies have found this to be the case in Queensland fruit flies (Tephritidae: Bactrocera tryoni Froggatt; �Q-flies�); male Q-flies allowed to self-regulate intake of yeast hydrolysate, a rich source of amino acids and vitamins used in most mass-rearing programmes (protein) and sucrose (carbohydrate), had greatly enhanced sexual performance compared with males provided only sucrose. While some yeast hydrolysate is clearly beneficial for the sexual performance of adult male Q-flies, the questions of what proportion of yeast hydrolysate in the diet is sufficient to yield full benefits, or is too much, have not yet been addressed. To address these questions, the present study assessed sexual performance and longevity of adult male Q-flies maintained on diets containing various proportions of yeast hydrolysate and sucrose. Male Q-flies maintained as adults on dry mixtures containing 9%, 17% or 25% yeast hydrolysate had mating probability, mating latency, copula duration and longevity similar to those provided yeast hydrolysate and sucrose in separate dishes and allowed to self-regulate intake. As in previous studies, while longevity was unaffected we found a marked reduction in sexual performance when the flies were completely denied access to yeast hydrolysate, and the few that did mate had relatively short copulations. At the other extreme, flies receiving diets with high levels of yeast hydrolysate (50%, 75%, 83% and 91%) suffered marked reductions both in longevity and in mating performance.

Abstract: Stenolemus bituberus is an araneophagic ��assassin bug�� (Heteroptera; Reduviidae; Emesinae) that typically is found living in spider webs. We documented the life history of S. bituberus in the field for 13 months, determining its developmental phenology and microhabitat characteristics as well as describing its mating and predatory behaviour. We also included a morphometric analysis of the instars. Our study revealed that S. bituberus is univoltine with five juvenile instars. Although S. bituberus is found in the webs of spiders from a wide range of genera, it is found most commonly in the webs of Achaearanea, Badumna, Pholcus, and Stiphidion. Multiple juveniles often were found on a single web, but adults tended to be more solitary. Stenolemus bituberus appears to have two distinct hunting strategies: ��stalking��, in which they slowly approach the spider, make contact and then strike; and ��luring��, in which they attract the spider within range by manipulating the silk with their legs.

Abstract: Feeding on yeast hydrolysate (a source of nitrogen) has a strong influence on the physiology and behaviour of the Queensland fruit fly (Q-fly), Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), affecting longevity, sexual maturation, oogenesis, and mating performance. In this study, we demonstrate that access to yeast hydrolysate also influences the development of attraction to cue-lure in Q-flies. We provided virgin Q-flies various periods of access to yeast hydrolysate (continuous, 48 h, 24 h, or deprived). Attraction of males to cue-lure was increased and occurred at an earlier age when they were fed yeast hydrolysate. Males given continuous access were strongly attracted to cue-lure at a younger age (8 days after emergence), but by 12 days after emergence attraction of males given access to yeast hydrolysate for 48 h did not differ from males given continuous access. Attraction by males deprived or given just 24 h access to yeast hydrolysate was always significantly lower than those of males with continuous access. Male attraction to cue-lure was highest in the early morning. While cue-lure is most often thought of as a male attractant, virgin female Q-flies were caught in cue-lure traps at dusk at ages when they are known to be sexually mature. We suggest that cue-lure or similar natural chemicals play a role in the Q-fly mating system. Irradiation used to induce sterility had no significant effect on attraction to cue-lure by Q-flies.

Abstract: Insect seminal fluid commonly comprises a complex cocktail of proteins and other biochemical components that migrate away from the female reproductive tract to sites elsewhere in the female body and elicit changes in female reproductive behaviour. The transfer of male seminal fluid molecules to reproductive and somatic tissues of the female Queensland fruit fly (�Q-fly�) Bactrocera tryoni is examined and some putative target sites identified. Male Q-flies are fed a diet containing radiolabelled (35S) amino acids, which are incorporated into male accessory gland products. Radioactivity diminishes within the accessory glands and increases in all assessed parts of the female body during copulation, indicating the transfer of these products into the female soma via the reproductive tract. There are significant changes in the absolute and proportional radioactivity profiles among female tissues over the next 22 h, with substantial reductions in the thorax and increases in the head. This is consistent with accumulation of behaviour-modifying male products at binding sites in the female head. Parallels can be drawn between the data in the present study and seminal fluid distribution profiles and receptor binding documented in other insects.

Abstract: Contestants can either assess their own resource-holding potential relative to their opponent (mutual assessment) or rely solely on the assessment of their own fighting ability (self-assessment). To discriminate between these possibilities, we staged dyadic territorial contests between �size-matched� male swordtails. These contests consist of a combination of ritualized displays and direct fighting. Although size differences were small, winners were larger than losers and smaller fish tended to be winners only when the size difference was negligible. Body size, however, did not influence contest duration and there was no increase in contest duration with mean body size; thus, there is no support for self-assessment in these animals. We also examined the effects of the sword, which comprises a sexually selected extension used in female choice that reduces swimming efficiency but increases acceleration. The length of the sword (adjusted for body size) did not differ between winners and losers; however, losers conceded earlier if the opponent had a large sword for its body size but this decision was independent of the loser�s own sword length. Losers thus assessed the swords of winners, which precludes self-assessment; however, because winners appeared not to assess the swords of losers, this does not fully support the idea of mutual assessment.

Abstract: Stenolemus bituberus Stål is an araneophagic Australian assassin bug (i.e. it preys on web-building spiders). As a step towards more thoroughly understanding the behaviour and predatory biology of this species, here we provide baseline information about development. During its development, there are 5 instars, with the 4th instar being the longest. The length of the 4th instar was consistent with this species� phenology in the �eld and corresponds to the winter months. Mortality during the 4th instar was higher than in any other instar. Sexes were similar in size until the 5th instar (width across eyes was greater for males than for females, a pattern continued into the adult stage). Overall, adult females tended to be larger than males. The growth rate between instars varied according to instar, although the transition from 5th instar to adult was generally associated with a decrease in growth rate compared with other transitions. Width across the eyes was the only metric that exhibited a sex difference in growth rate, with males growing more than females during the transition from 4th to 5th instar.

Abstract: An unresolved question in sexual selection research is whether different secondary sexual traits are developmentally independent or instead whether their degree of expression is a manifestation of a general resource pool (i.e., condition) within the organism. If degree of expression of different sexual traits reflects ability to accumulate condition, then covariation should exist across genotypes in the expression of these traits, even if they are very different in kind. Here we present evidence for predicted covariation between morphological (sex comb size) and behavioral (courtship song) sexual traits among genetic lines of Drosophila bipectinata Duda extracted from a natural population. There is evidence that both these traits in Drosophila are condition dependent and subject to sexual selection. We detected significant body size�independent differences in comb size among 32 lines. Replicate lines exhibiting relatively high and low values of comb size were then subjected to analyses of courtship song. High sex comb lines exhibited shorter mean burst period and shorter mean burst duration than low sex comb lines. These song differences occurred only during the distant pursuit phase of male courtship and existed despite factoring out individual variations in sex comb size, the trait on the basis of which test lines were originally chosen. The results verify the prediction of an association between condition-dependent secondary sexual traits across genotypes and, therefore, support the existence of an overall genetic quality related to condition acquisition.

Abstract: Molecules in male seminal fluid transferred to female insects during mating can have potent effects on their subsequent sexual and reproductive behaviour. Like many other tephritids, female Queensland fruit flies (Bactrocera tryoni) typically have diminished sexual receptivity after their first mating. Also, copulations of females that do remate tend to be shorter than those of virgins. We here find that virgin females injected with small doses (0.1, 0.2 or 0.5 male equivalents) of extracts from the male reproductive tract accessory tissues, which consist of male accessory glands, ejaculatory apodeme and ejaculatory duct (AG/EA/ED), have diminished receptivity and short copula duration very similar to naturally mated females. In contrast, virgin females injected with saline or with high doses of AG/EA/ED (1 or 2 male equivalents) that likely exceed the range of natural variation retain the higher levels of sexual receptivity and longer copulations of un-injected virgins. We conclude that reduced sexual receptivity and shorter copulations of mated female Q-flies are mediated by products in the male seminal fluid derived from the male reproductive tract accessory tissues.

Abstract: In evolutionary biology, fluctuating asymmetry (FA) is thought to reveal developmental instability (DI, inability to buffer development against perturbations), but its adaptive and genetic bases are being debated. In other fields, such as human clinical genetics, DI is being assessed as incidence of minor morphological abnormalities (MMAs) and used to predict certain fitness outcomes. Here, for the first time, we combine these complementary measures of DI in sexual selection and quantitative genetic studies of a natural population. Comprehensive multivariate analyses demonstrate that FA and MMAs in a condition-dependent sexual ornament, the male Drosophila bipectinata sex comb used in courtship, are sole significant targets of selection favouring their reduced expression in New Caledonia. Comb FA and MMAs are positively correlated, confirming that each are linked to a common buffering system. Ornament size and DI (as FA and MMAs) are positively correlated, genetically and phenotypically, contrary to theoretical expectation of negative size-FA scaling under the assumption that FA reveals overall genetic quality. There exists significant additive genetic variance for MMAs, demonstrating their evolutionary potential. Ornament DI in New Caledonia is markedly elevated compared with populations where such selection was not detected, suggesting that the increased population-level DI is capacitating adaptive evolution.

Abstract: Female animals that use sperm from a single mating to fertilize eggs over an extended period require efficient mechanisms for sperm storage and use. There have been few studies of these mechanisms in tephritid flies. Mating, copula duration, sperm storage and sperm usage patterns are assessed in an Australian tephritid, the Queensland fruit fly (Bactrocera tryoni; a.k.a. �Q-fly�). In particular, the present study investigates whether each of these aspects of mating varies in relation to female size or male size, whether sperm storage patterns change over time after mating (1, 5, 10 and 15 days), and the relative roles of the ventral receptacle and the two spermathecae as sperm storage organs. Large females are more likely to mate than are small females, and are also more fecund in the first 5 days after mating. Females are more likely to store some sperm and, among those that store some sperm, store more sperm if their mate is large. Most sperm are stored in the spermathecae (median = 97%), often with high levels of asymmetry between the two spermathecae. Asymmetry of sperm storage is related to number of sperm stored, but not to male or female size. Total number of stored sperm declines over the 15 days after mating, but this decrease in sperm numbers only reflects changes in the spermathecae; numbers of sperm in the ventral receptacle remain unchanged over this period. As a consequence, the proportion of total sperm stored in the spermathecae declines relative to the ventral receptacle. These results are consistent with a system in which small numbers of sperm are maintained in the ventral receptacle for fertilizations, and are replenished by sperm from the spermathecae as required. Sperm distribution and usage patterns in Q-flies are comparable with recent findings in medflies, Ceratitis capitata, but differ markedly from patterns found in several Anastrepha species.

Abstract: Adult diet is an important determinant of sexual activity in many tephritid fruit flies. Whether availability of protein (hydrolysed yeast) in addition to sucrose influences sexual activity or longevity of male and female Queensland fruit flies (Bactrocera tryoni Froggatt, �Q-flies�), and whether irradiation of flies as pupae modifies their dietary needs is investigated. Previous studies on groups of flies have suggested that protein is required for sexual maturation of females but not males. By contrast, this study of individual flies demonstrates that protein in the adult diet provides a massive boost to sexual activity of both males and females. Mating probability increases with age from 4-14 days as the flies began to mature. However, mating probability reaches much higher levels when the flies are provided with protein. While males and females mate at similar rates when provided with protein, females suffer a greater reduction in mating probability than males when deprived of protein. In addition to increased mating probability, access to dietary protein is associated also with reduced latency from onset of dusk until copulation. Further, young male flies with access to dietary protein have longer copula duration than males fed only sucrose. Irradiation of flies as pupae has no apparent effect on mating probability, the latency to copulate or copula duration. However, when deprived of protein, sterile flies (especially males) suffer a greater reduction in longevity than fertile flies. Overall, access to dietary protein increases longevity for both males and females, although females live longer than males on both diets. These findings suggest that pre-release provision of dietary protein has the potential to greatly enhance the efficacy of Q-flies used in the Sterile Insect Technique.

Abstract: Animals often evolve complex signals to enhance their detectability by intended receivers. But signals that are more detectable by intended receivers may also be more likely to be intercepted by others, including predators. Courtship signaling in male Schizocosa ocreata wolf spiders (Lycosidae) includes morphological traits (prominent foreleg tufts) and active behaviors that together produce a complex signal with simultaneous broadcast of visual and seismic components. Females respond more readily to males with large tufts and are more likely to respond when multiple modalities (visual and seismic) are present in a complex signal. These spiders cooccur with active predators that may intercept these conspicuous courtship signals and use them as hunting cues. We used video/seismic playback to experimentally isolate and manipulate aspects of the complex signal produced by male S. ocreata. We found that increasing the size of a visual signal (male tufts) and increasing the complexity of the courtship signal by adding a second modality (visual plus seismic versus visual alone) increased the speed with which a common predator, the jumping spider Phidippus clarus (Salticidae), responded to playbacks of courting male S. ocreata. These results indicate that the benefits of increased signaling efficacy of large visual signaling ornaments and complex, multimodal signaling may be countered by increased predation risks.

Abstract: The sterile insect technique (SIT) is increasingly being used around the world to control Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), the Mediterranean fruit fly as part of an area-wide integrated approach. One option that may improve the effectiveness of the SIT, by increasing the sexual competitiveness of released sterile males, consists of feeding males protein during the post-teneral stage, a diet that increases sexual performance of wild males. We examine the effects of diet on the successive hurdles males must overcome in order to inseminate females, i.e., joining leks, copulating females, having their sperm stored and inhibition of female remating. In addition, we address the effects of diet on post-release foraging success, longevity, and the ability to withstand starvation. While protein feeding universally increases the sexual success of wild males, its effect on sterile males varies with strain, experimental settings, and environmental conditions. In some cases, treatments that resulted in the best sexual performance were significantly associated with increased vulnerability to starvation. However, no particular diet affected the ability of sterile males to find nutrients in the field when these where available. We suggest it may be better to release relatively short-lived flies that are highly competitive, rather than long-lived, sexually ineffective ones.

Abstract: In animal contests, individuals can either engage in mutual assessment of both their own and their opponent�s resource-holding potential (RHP) and adjust their behaviour according to estimated differences, or instead persist in accordance with thresholds determined by assessment of just their own RHP. We examined the predictions of alternative mutual assessment and self-assessment models for decision rules in contest resolution during struggles between males over females in precopula in the amphipod Gammarus pulex. Contest duration was positively related to the weight of the loser but not the weight of the winner. Our results support the hypothesis that males rely on information about their own RHP in determining contest behaviour and do not use information about their opponent. Fighting was energetically costly, and energy reserves were depleted during contests. Contest duration was associated with the physiological state of the loser (but not the winner) at the end of the contest, and to a lesser extent his size, further supporting self-assessment.

Abstract: Male Schizocosa ocreata wolf spiders court females using displays that involve dramatic waving motions of their ornamented forelegs. In nature males are often found missing one, and sometimes both, of these legs. We here find that, when exposed to female draglines, males missing these signalling appendages perform a high intensity courtship element (�jerky tapping�) at a much greater rate than intact males. Loss of forelegs was also associated with changes in chemoexploration activity, tendency to stand stationary, and performance of a low intensity courtship element (�tapping�). The age of the virgin female from which draglines were collected also had an important influence on male courtship behaviour; males on the draglines of old females were less likely to court and, if they did court, did so at a lower rate. These data indicate that courtship behaviour of male S. ocreata is flexible, varying both with the state of the male himself and the state of the female whose draglines he has encountered. Such individual courtship flexibility raises challenging questions of what processes and trade-offs underlie male courtship decision-making, and whether autotomy-induced changes in courtship activity represent adaptive compensation.

Abstract: Males of many animal species are reproductively limited by the difficulty and time costs of finding mates. Males of such species should be selected to take advantage of any cues that might reveal the location of prospective mates. Cues to female location are not restricted to those produced by females, but might also include the highly apparent courtship displays of males that have already found a female. By �eavesdropping� on these courting rivals, initiating sexual displays when courting rivals are detected (i.e., social facilitation of displays), males might effectively exploit the mate-searching efforts of their rivals. We tested the possibility that male Schizocosa ocreata wolf spiders exhibit social facilitation of courtship behaviors using a combination of live behavioral trials and video playback with single stimulus presentations. When exposed to visual cues from another male, male S. ocreata can discern the presence of another individual whether that individual is courting or not. However, we found no evidence of social facilitation of courtship or chemoexploratory behaviors in response to seismic or visual cues presented in isolation or combined. While complex, multi-modal, male courtship signals are important in mate choice by female S. ocreata, males do not appear to use these cues to socially facilitate their own courtship.

Abstract: Reproductive success of male insects commonly hinges both on their ability to secure copulations with many mates and also on their ability to inseminate and inhibit subsequent sexual receptivity of their mates to rival males. We here present the first investigation of sperm storage in Queensland fruit flies (Tephritidae: Bactrocera tryoni; a.k.a. 'Q-flies') and address the question of whether remating inhibition in females is directly influenced by or correlated with number of sperm stored from their first mates. We used irradiation to disrupt spermatogenesis and thereby experimentally reduce the number of sperm stored by some male's mates while leaving other aspects of male sexual performance (mating probability, latency until copulating, copula duration) unaffected. Females that mated with irradiated rather than normal males were less likely to store any sperm at all (50% vs. 89%) and, if some sperm were stored, the number was greatly reduced (median 11 vs. 120). Despite the considerable differences in sperm storage, females mated by normal males and irradiated males were similarly likely to remate at the next opportunity, indicating (1) number of sperm stored does not directly drive female remating inhibition and (2) factors actually responsible for remating inhibition are similarly expressed in normal and irradiated males. While overall levels of remating were similar for mates of normal and irradiated males, factors responsible for female remating inhibition were positively associated with presence and number of sperm stored by mates of normal but not irradiated males. We suggest seminal fluids as the most likely factor responsible for remating inhibition in female Q-flies, as these are likely to be transported in proportion to number of sperm in normal males, be uninfluenced by irradiation, and be transported without systematic relation to sperm number in irradiated males.

Abstract: Male Schizocosa ocreata wolf spiders court females using displays that involve dramatic waving motions of their ornamented forelegs. In nature males are often found missing one, and sometimes both, of these legs. We here find that, when exposed to female draglines, males missing these signalling appendages perform a high intensity courtship element (�jerky tapping�) at a much greater rate than intact males. Loss of forelegs was also associated with changes in chemoexploration activity, tendency to stand stationary, and performance of a low intensity courtship element (�tapping�). The age of the virgin female from which draglines were collected also had an important influence on male courtship behaviour; males on the draglines of old females were less likely to court and, if they did court, did so at a lower rate. These data indicate that courtship behaviour of male S. ocreata is flexible, varying both with the state of the male himself and the state of the female whose draglines he has encountered. Such individual courtship flexibility raises challenging questions of what processes and trade-offs underlie male courtship decision-making, and whether autotomy-induced changes in courtship activity represent adaptive compensation.

Abstract: Male Schizocosa ocreata spiders court females with synchronous visual and seismic signals. We tested whether male S. ocreata modify their courtship in relation to light environment, and associated utility of the visual signals. Males were generally more active and more likely to perform the major courtship element (�jerky tapping�) when in the light. One courtship element (�arching�) was only observed in the light while another (�leg-extend�) was only observed in the dark. Courtship in the dark retained �visual� components, suggesting spiders cannot disengage visual components of multi-modal display even when superfluous. Once initiated, there was no evidence that performance rate or time spent in each courtship element differed in the light and in the dark.

Abstract: Female Mediterranean fruit flies, Ceratitis capitata (Wiedemann), from the sterile-male rearing facility in El Pino, Guatemala, were exposed to broadcasts of wing-fanning vibrations recorded from males engaged in calling behavior to investigate the feasibility of developing a female-selective acoustic trap. The recorded signals had frequent amplitude fluctuations and peak frequencies approximately 350 Hz, typical of signals observed in previous studies of Mediterranean fruit fly acoustic behavior. Females did not exhibit long-distance phonotaxis, but remained near a speaker significantly longer when the sounds were broadcast at 103-107 dB than when the speaker was silent. In addition, significantly higher percentages of females were captured by yellow adhesive traps next to a broadcasting speaker than by traps next to a silent mimic. Additional bioassays were conducted with synthetic, 350-Hz tones produced by a thermoacoustic tube as well as with silent mimics of the different sound sources to examine the relative responsiveness of female Mediterranean fruit flies to traps with different acoustic and visual features. The visual attributes of the different sound source assemblies significantly affected capture rates. The range over which the broadcast significantly increased the percentage of female captures was <0.5 m, which may limit the utility of these acoustic cues in large-scale trapping programs. However, the findings of this study do justify further testing of whether optimized short-range acoustic signals could be used to augment longer range pheromonal and visual cues to improve the efficacy of female-selective traps.

Abstract: Contests between rivals placing similar value on the resource at stake are commonly won by the rival having greater 'Resource holding potential' (RHP). Mutual assessment of RHP difference between rivals is usually expected as an economical means of resolution; weaker rivals can retreat when they detect their relative inferiority, thereby avoiding costly, futile, persistence. Models of contest resolution that entail retreat decisions based on estimates of RHP difference predict that contest duration diminishes as RHP difference between rivals increases because the asymmetry is more readily detected. This prediction appears to have been fulfilled in contests of diverse taxa, generating widespread support for assessment of RHP differences in contests. But few studies have considered alternatives in which each rival simply persists in accord with it's own RHP ('own RHP-dependent persistence'). In contests decided by own RHP-dependent persistence in which costs only accrue through each rival's own actions, weaker rivals retreat first because they are inherently less persistent and contest duration depends primarily on the weaker (losing) rival's RHP rather than RHP difference between the rivals. We show here that the analyses most commonly employed to detect effects of RHP difference cannot discriminate between these alternatives. Because RHP difference between rivals tends to be correlated with RHP of the weaker rival in a pair, negative relationship between RHP difference and contest duration may be generated even when decisions of retreat are not based on estimated RHP difference. Many studies purporting to show negative relationship between RHP difference and contest duration may actually reflect an incidental association between weaker rival RHP and RHP difference. We suggest statistical and experimental approaches that may help to discriminate between effects of weaker rival RHP and true effects of RHP difference. We also discuss whether 'true' negative effects of RHP difference on contest duration always reflect retreat decisions based on estimated RHP differences.

Abstract: For potentially cannibalistic animals such as spiders, the ability to recognize and avoid kin and/or preferentially cannibalize non-relatives would permit exploiting conspecifics as prey while minimizing loss of inclusive fitness. We investigated the effects of relatedness and availability of alternative food on cannibalism tendency in pairs of juvenile Hogna helluo (Walckenaer), a North American wolf spider (Araneae: Lycosidae). For second-instar spiderlings (dispersing stage), cannibalism was more likely among pairs of non-sibs than pairs of sibs and, interestingly, was also more likely when other prey were available. We found no evidence of increased cannibalism in pairings involving broods of greatest average size disparity, indicating that size differences are unlikely to explain differences in cannibalism tendency. Additionally, the relative number of deaths from cannibalism or other causes did not increase with increasing risk of starvation. For third-instar spiderlings, which had lived independently of their mother and sibs following dispersal, cannibalism rates were very high in all treatments and there were no significant effects of relatedness or food availability. Our results suggest that spiders with predominantly solitary lifestyles may bias cannibalism toward non-kin during the juvenile associative period, and that this effect is lost in the subsequent instar. Results are discussed in the context of several potential mechanisms that might result in differential cannibalism.

Abstract: Signal costs, and associated trade-offs, are widely thought of as fundamental to the evolution and maintenance of reliable signals. Contrasting this view, the amplifier mechanism postulates that signals may be deemed reliable by design rather than by costs. Although the idea is not new, investigation of amplifier signals in nature remains scant. Here we show that displays and body markings on the Mediterranean tarantula, Lycosa tarantula (L.) (Lycosidae) are consistent with interpretation as amplifiers of size and body condition. The size of tibia and abdomen ventral markings (which alternate dark and pale patterns) presented to rivals during contests are highly correlated with body size and condition respectively. Abdomen markings have the additional feature of placement on a region especially influenced by abdomen distension and therefore has greater proportional variation than the underlying amplified trait. In spite of the differences in size and in body patterns between spiders of two isolated and ecologically different populations, correlation between body marking and dimensions, and relatively high proportional variation of the abdomen markings, was maintained, probably reflecting the adaptive value of these traits. We conducted a feeding experiment which showed that the abdominal markings enlarged (stretched with abdomen distension) at a higher rate if spiders were provided with more food, further supporting the idea that this marking amplifies body condition.

Abstract: An animal's ability to win intra-sexual conflicts is often determined by the combined influence of several different traits, such as size, experience, residency and prior injury. When each of two (or more) asymmetries favours a different rival, the outcome of a conflict will reflect each asymmetry's contribution to overall status. We investigated the interacting effects of size difference and prior loss of forelegs (a common injury in nature) on ability of males to win intra-sexual conflicts in Trite planiceps, a New Zealand jumping spider (Salticidae). When both rivals were intact, the probability of the larger rival winning increased with size difference between the rivals. When rivals were of matching size, injury was a strong predictor of outcome; intact spiders beat rivals missing one or both forelegs and spiders missing one foreleg beat rivals missing both forelegs. During conflicts between spiders that differed both in size and in injury state, these two variables had combined effects on outcome. The tendency for larger rivals to win increased with size difference but the probability of larger rival winning diminished if the larger rival of the pair was the more injured. We used inverse prediction from logistic regression models to quantify the size advantage that is sufficient to offset the disadvantage of prior injury.

Abstract: Foraging decisions may reflect a trade-off between food intake and safety and can also be influenced by the animal's internal state. Foraging in the web-building spider Stegodyphus lineatus depends on a capture web associated with a retreat (the nest). The relocation of nests, including the take-over of conspecific nests, may be viewed as a foraing decision, which depends on risk of exposure, cost of silk production and hunger state. We investigated a possible state-dependent trade-off in nest site choice of S. lineatus spiderlings. The philopatric nature of S. lineatus implies a high risk of encounters with potentially cannibalistic conspecifics and a potential loss of inclusive fitness because encountered conspecifics are likely to be kin. To test for state dependence of foraging decisions, we compared preferences of well-fed and hungry spiders for their own nests and those of siblings and nonsiblings. We expected satiated spiders to prefer their own to conspecific nests and hungry spiders to choose the risky option of a conspecific nest. Since S. lineatus is less aggressive towards kin, we tested the ability of spiders to discriminate kin by silk-bound cues. Because of this reduced aggression, preference for kin nests should be safer than preference for nonkin nests. A strong preference for self-nests demonstrated self-recognition in well-fed spiders. However, neither well-fed nor hungry spiders discriminated between nests of siblings and nonsiblings. Well-fed spiders preferred self-nests to empty chambers, but showed no discrimination between nonself-nests and empty chambers. Hungry spiders showed a reduced preference for self-nests, suggesting that hunger elicits a more risky foraging strategy. A tendency of hungry spiders to adopt the nests of conspecific spiders may reflect a silk-saving strategy. We conclude that S. lineatus spiders show state-dependent decision making in nest site selection.

Abstract: To realize their reproductive potential, male Mediterranean fruit flies must run a gauntlet of behavioral challenges during which they may be edged out by rivals, or fail the acid test of female choice. Milestones on this perilous road include: 1. showing up at a lek site 2. emitting pheromone 3. performing courtship 4. copulation 5. sperm transfer & storage 6.fertilization of eggs 7. preventing or delaying female re-mating. In a number of recent studies focused on each of these steps we tested the hypothesis that post-teneral male nutrition affects male sexual performance. Both field and laboratory data indicate that protein nutrition increases a male�s probability of emitting pheromone in a lek. Field cage data show that protein fed males are also more likely to engage in critical elements of close-range courtship, and evidence from several studies indicate that protein fed males are more likely to copulate than sugar-fed or starved flies. As to sperm transfer and storage, we find that the context of the experiment and the source of flies used affect the outcome, suggesting that diet alone cannot explain the variability in the probability of sperm being transferred, and in the amount of sperm transferred. To date we have not studied effects of male diet on fertilization. Nevertheless, we have shown that male diet significantly affects female receptivity- females whose first mate was protein-deprived, re-mate sooner than females whose first mate was protein-fed.

Abstract: The Sterile Insect Technique (SIT) is used in many regions worldwide to manage wild populations of the Mediterranean fruit fly ('medfly'), an important pest species. This technique relies on released sterile males out-competing their wild counterparts in fertilizing ova of wild females. Numerous studies have investigated the ability of sterile males to secure copulations, an essential step toward overall success. Here we progress further along the mating sequence by studying reproductive barriers that may remain ahead of sterile males that manage to secure copulations in field cage experiments and whether ability to pass these barriers is influenced by a male's age, diet and size, or the size of his mate. Amongst those virgin males that succeeded in copulating, both the number of sperm stored by mates and the chances of having any sperm stored at all decreased with age. Sperm tended to be stored asymmetrically between the female's two spermathecae, and this tendency was more apparent when few sperm were stored. In accord with effects of male age on number of sperm stored, sperm of older males were stored more asymmetrically than that of young males. We found no evidence that male size, male diet or female size influenced copula duration, number of sperm stored or allocation of sperm between the female�s two spermathecae. The decline in number of sperm stored as males aged was not accompanied by age-dependent changes in copula duration, indicating that copula duration and insemination success are not deterministically linked. We discuss these results in light of their relevance to SIT and the medfly mating system.

Abstract: Animals are commonly expected to assess each other during contests to economically identify relative status. Escalated or long contests are expected to arise mainly when rivals have difficulty discriminating small differences. Results of the present study of male-male contests in Plexippus paykulli, a jumping spider (Salticidae) with acute vision, are not in accord with this widely held view. Despite the typical finding that size-advantaged rivals are more likely to win contests and that this tendency increases with size disparity, contest dynamics suggest that these tendencies are achieved in the absence of direct size assessment. In contests between different-sized spiders, maximum escalation and overall duration are predicted by absolute size of the size-disadvantaged spider (usually the loser) rather than difference in size between the rivals. This result suggests that spiders base decisions of persistence on their own size such that size-disadvantaged rivals usually reach their limits first, and then retreat. This interpretation is further supported by findings that maximum escalation and total duration were both positively related to size in contests between size-matched spiders. Spiders were more likely to win if they oriented and displayed first, and longer, more escalated, contests ensued if the size-disadvantaged spider was the first to orient and display. Proximity of rivals at contest outset also influenced contest dynamics, but not outcome.

Abstract: The sterile insect technique (SIT) is used as an environmentally friendly means of suppressing Mediterranean fruit fly (Ceratitis capitata; 'medfly') populations in the Arava valley of Israel. This technique depends on released sterile males effectively wresting away the reproductive potential of wild, fertile, males. Studies carried out in other countries have indicated that sterile males may sometimes be of inferior sexual competitiveness when compared with their wild counterparts and that this may inhibit SIT efficacy. In this study, we used field-cage experiments to investigate the sexual competitiveness of sterile male medflies (genetic sexing strain Vienna 4/Tol-94) produced and shipped from Guatemala in the presence of wild males in Israel. We also checked whether pre-release chilling affects their sexual success. We found that sterile and wild males were similar in mating frequency, latency until mating, insemination probability and duration of copulations during which no sperm were stored. There was, however, weak evidence that copulations involving sperm storage were shorter for sterile males. Chilling did not influence any element of male sexual performance. In both experiments, copulations culminating in sperm storage by females were longer than copulations that failed, suggesting that processes occurring early on in copulation may sometimes be the source of sexual failure. Overall, these results indicate a high standard of vigor in the sterile male medflies used in the SIT program presently under way in Israel.

Abstract: 1. In the present study we test the hypothesis that in insects which invest considerable energy in sexual displays and courtship, foraging successfully for food affects their subsequent performance and copulatory success in leks. 2. We investigate the interactions between individual size and diet on initiation of lekking behaviour and copulatory success of male Mediterranean fruit flies, Ceratitis capitata (Diptera: Tephritidae). 3. We found that protein-fed males were heavier, and contained more protein and less lipid reserves than protein-deprived males. protein-fed males were more likely to emit pheromone in leks, and consequently, were more likely to copulate than protein-deprived males. Furthermore, protein-fed males tended to start calling earlier than their nutritionally deprived competitors. Though size was not related to initiation of lek behaviour, large males were more likely to copulate than small males. Amongst protein-fed males, large individuals tended to mate earlier than smaller ones. 4. We suggest that generally, in lek mating systems, where a considerable investment of time and energy is required by males, foraging successfully for nutritional resources prior to engaging in territorial or courtship behaviour is essential for reproductive success.

Abstract: In the Mediterranean fruit fly (Ceratitis capitata Weidemann, 'medfly'), a lekking tephritid, evidence from laboratory studies of flies from laboratory strains suggests that copulation is shorter, and sperm storage more abundant, if males are large or protein-fed, and that copulation is longer when females are large. In addition, sperm tend to be stored asymmetrically between the female's two spermathecae and this asymmetry declines with abundance of stored sperm. The primary objective of this study was to investigate whether these trends persist in other experimental contexts that bear closer resemblance to nature. Accordingly, we carried out experiments in a field-cage using males derived as adults from a wild population and virgin females reared from fruit infested in nature. Results of this study were consistent with laboratory studies in that copula duration increased with female size, that sperm were stored asymmetrically between the females� spermathecae, and that this asymmetry declined with number of sperm stored. However, we also found some previously unreported effects of female size; large females stored more sperm and stored sperm more asymmetrically between their two spermathecae than did small females. Unlike the laboratory studies, copula duration and sperm storage patterns were unaffected by male size and diet. This may be due to overwhelming variation from other sources in the wild-collected males used.

Abstract: The question of why receivers accept a selfish signaller's message as reliable or 'honest' has fuelled ample controversy in discussions of communication. The handicap mechanism is now widely accepted as a potent constraint on cheating. Handicap signals are deemed reliable by their costs: signallers must choose between investing in the signal or in other aspects of fitness. Accordingly, resources allocated to the signal come to reflect the signaller's fitness budget and, on average, cheating is uneconomic. However, that signals may also be deemed reliable by their design, regardless of costs, is not widely appreciated. Here we briefly describe indices and amplifiers, reliable signals that may be essentially cost free. Indices are reliable because they bear a direct association with the signalled quality rather than costs. Amplifiers do not directly provide information about signaller quality, but they facilitate assessment by increasing the apparency of pre-existing cues and signals that are associated with quality. We present results of experiments involving a jumping spider (Plexippus paykulli) to illustrate how amplifiers can facilitate assessment of cues associated with physical condition without invoking the costs required for handicap signalling.

Abstract: Previous laboratory studies of Mediterranean fruit flies, Ceratitis capitata (medflies), have identified large size and protein feeding as positive influences on the ability of males to secure copulations. In this study, we investigated whether large and protein-fed males experience additional advantages in terms of amount and distribution of sperm stored by mates. We also examined relationships between copula duration and sperm storage. Mates of large and protein-fed males were more likely to store sperm and to store more sperm than mates of small and protein-deprived males. Probability of sperm storage was associated with copula duration; all copulations lasting less than 100 min failed whereas 98% lasting longer than 100 min succeeded. Copulations involving sperm storage were longer if males were small or protein deprived or if the female was large, although there was no evidence of a relationship between copula duration and total sperm storage. Evidence from related studies suggests that variation in latency until sperm transfer, caused by size and diet, is a likely explanation for varying copula duration. Sperm tended to be stored asymmetrically between the female's two spermathecae, consistent with a mating system in which females maintain isolated populations of sperm from different males and later select between them. Storage was less asymmetric when large numbers of sperm were stored but there was little evidence that male size or diet affected this asymmetry. It is uncertain whether postcopulatory advantages of large and protein-fed male medflies arise from female preferences or male dominance through coercion or force. Copyright 1999 The Association for the Study of Animal Behaviour.

Abstract: Previous studies have reported considerable variation in copula duration in the Mediterranean Fruit Fly (medfly), Ceratitis capitata Weidemann (Diptera: Tephritidae). Presently, however, this variation is largely unexplained. In this study we measure copula duration in two medfly strains used in applied research in Israel and examine how much of the variation in copula duration is due to the strain, age, the time of day the mating begins and the relative size of the mating pair. We found the following: flies of a strain reared in the laboratory since 1976 (Vienna) copulated for longer than flies of a strain collected in 1969 and periodically refreshed with wild males (Sade); older flies copulated for longer than young flies; and pairs in which males were smaller than females copulated for longer than pairs in which males were larger or the sexes were more evenly size-matched. The time of day the mating commenced (morning vs afternoon) had no effect. We discuss potential mechanisms underlying these variations in medfly copula duration.

Abstract: The natural history and intraspecific interactions of Trite planiceps, a common New Zealand jumping spider (Salticidae), are described for the first time and discussed in relation to this salticid's unusual microhabitat - the rolled-up leaves of New Zealand flax (Phormium tenax) and similar plants. In many respects, T. planiceps' display and mating behaviour resembles other salticids. Males have conditional courtship and mating tactics, and the tactics used depend on the female's maturity and location. If in the light, the male uses vision-based courtship and mates in the open; if at a nest (inside a rolled-up leaf), the male uses vibratory courtship and mates inside the rolled-up leaf; if the female is immature but within c.10 days of maturing, the male cohabits until the female matures and then mates inside the rolled-up leaf. Regardless of which mating tactic is used, after males mount females there is a phase during which the pair are in physical contact and communicate using tactile signals ('post-mount courtship'). Other sex and age classes of T. planiceps also communicate using visual displays when in light, away from rolled-up leaves, and also sometimes employ tactile signals when at nests or during escalated contests in the light. In addition to these typical salticid characteristics, T. planiceps has some atypical display behaviours that appear to be adapted for communicating in its unusual habitat. Even when no conspecific has been encountered, T. planiceps males sometimes display when approaching openings of rolled-up leaves occupied by conspecific females. These displays closely resemble visual displays used while facing a conspecific in the light. Later, while entering the cavites within rolled-up leaves and while moving about inside simulated rolled-up leaves (glass tubes kept away from visible light and observed using infra-red video), males and females use vibratory displays, tapping the leaf surface with Legs I and vibrating their abdomens, even when no conspecific has been encountered. Finally, when spiders interact within simulated rolled-up leaves, they appear to communicate using both tactile signals and vibratory signals that are transmitted through nests or leaf surfaces. Many other salticids use nests as a medium for transmission of vibratory signals. However, T. planiceps' use of the leaves forming its nesting microhabitat for this function is unusual. This is the first study in which infra-red video has been used to observe interactions between salticids under conditions of total darkness for the spider, and also the first report of a salticid possessing a display repertoire for use in darkness but away from nests. We emphasise adaptation for typical habitat as a partial explanation for species differences in salticid communication systems.

Abstract: Jumping spiders (Salticidae) are well known for their complex visual hunting behavior, but this is the first comparative study investigating their ability to catch prey in the absence of visual cues. When tested with vision occluded inside tubes, where spiders and prey (house flies, Musca domestica, and fruit flies, Drosophila spp.) could not easily evade each other, each of 42 salticid species tested caught prey in at least one of five different procedures used. Some salticids caught flies less frequently or were less aggressive when tested in petri dishes, where spiders and flies could easily evade each other. For both types of arena and prey, there were significant species differences in both success at prey-capture and tendency to respond aggressively when first contacted by flies. Additionally, there was significant positive correlation between success at catching prey and tendency to act aggressively when first contacted. Salticids resembled short-sighted spiders from other families by only attempting to catch flies when physically contacted, and by rapidly leaning forward ('lunging') to catch prey rather than leaping as they do when visual cues are available. We discuss circumstances in nature when an ability to catch prey in the absence of visual cues might be used by salticids.

Abstract: Trite planiceps Simon 1899, a common New Zealand jumping spider (Salticidae), lives in the cavities formed by rolled up leaves of New Zealand flax (Phormium tenax) and similar plants. This study presents evidence that T. planiceps males use cues from females' draglines deposited on the outside of these rolled up leaves when searching for females hidden from view inside. In choice tests, T. planiceps males preferentially associated with draglines deposited by conspecific females rather than areas lacking draglines. In contrast, females did not discriminate between areas with and without males' draglines and neither males nor females discriminated between areas with and without same-sex conspecifics' draglines. Additionally, T. planiceps males found openings and entered the cavities within rolled up leaves occupied by females in nature sooner when leaves were tested within 24 hours of collecting (dragline cues deposited on leaves in nature) than after the same leaves had been cleaned and aged for 7 days (dragline cues removed). Shorter latency to finding of leaf openings was restored after the same leaves were subsequently occupied by females in the laboratory (dragline cues replaced). The specific cues detected by T. planiceps males are probably pheromones loosely bound to females' draglines.

Abstract: In the laboratory, Trite planiceps (Salticidae) delayed oviposition when conditions simulating their natural oviposition sites were unavailable. Timing of oviposition in T. planiceps appears to be determined in part by the suitability of available sites. By being able to discern site suitability and delay oviposition when suitable sites are not available, a spider in nature would gain time to find a better site. This appears to be amongst the first studies to investigate the rules underlying timing of oviposition in spiders.

Abstract: In support of the hypothesis "brood-attendance by maternal jumping spiders (Salticidae) functions as brood-defense", broods of Trite planiceps are shown to suffer increased predation in nature when maternal females are removed. Apparent predators of unattended T. planiceps broods are identified in nature, and that these species eat T. planiceps eggs and post-embryos is confirmed in the laboratory. Trite planiceps males and females not attending broods of their own ate the eggs and post-embryos of conspecifics in the laboratory but females with their own broods did not, indicating that predation of conspecific's broods is suppressed by maternity.

Abstract: The prey-catching behaviour of Diaea sp., a thomisid from New Zealand, is documented for the first time. This is the first detailed report of web building and predatory versatility in a thomisid spider. Diaea sp. is neither simply a web-building spider nor simply an ambush non-web-building spider. Instead, individual spiders of this species practise both of these prey-catching methods.

Abstract: A new species of stiphiid spider belonging to the endemic New Zealand genus Cambridgea is described from Riccarton Bush, Christchurch, and Kaituna Valley, Banks Peninsula. Cambridgea quadromaculata n. sp. is large, active, and apparently makes no substantial webs. Both samples were from wet habitats vulnerable to intermittent flooding. Characters that distinguish C. quadromaculata from other large Cambridgea are specified. Attention is drawn to a possible ecological and systematic parallel between Cambridgea and the European genus Tegenaria Latreille (Agelenidae).

Abstract: Four species of diurnal jumping spiders (Salticidae) and one species of nocturnal clubionid spider are shown to alternate turns in complete darkness. Alternation of turns enables these spiders to approximate a straight path in the absence of visual cues either for pre-setting a course or as feedback during locomotion. How these spiders might use this ability in natural conditions is discussed.