Abstract: Phosphaenus hemipterus (Fourcroy, 1785) is considered a very rare glow-worm and has conse- quently been studied very little. This paper unites the scattered data on the known distribution of P. hemipterus and gives descriptions of habitat use, phenology and activity patterns at recently discovered sites in Belgium. Adult males were found from mid-June to mid-July and were most abundant on warm days, with a clear diurnal activity pattern. Only a few adult females were found, mainly around dusk and in or near crevices. Larvae are mainly nocturnal and glow spontaneously as do most lampyrid larvae, but many were also found during the day. The larvae appear to feed only on earthworms. Typical features of the habitat of P. hemipterus are loamy soils and abrupt transitions from dense vegetation into bare patches. Apparently many of these features are present in areas with severe human disturbance such as in gardens, parks, car parks and at field edges. However, most survey studies on glow-worms are carried out in nature reserves, which may explain why P. hemipterus is mostly missed. The species may actually be not as rare as presumed, and, moreover, it occurs in areas that are not considered important for conservation managment.

Abstract: Bioluminescence most likely evolved under selection from the visually guided behaviours of co-occurring organisms, in particular that of predators. Many possible functions of light signals have been proposed and some are supported, but whatever their function may be, they make an easy target of the emitter unless it is defended. Therefore, we want to emphasise that in many cases bioluminescence can only have evolved through a defensive function. If this were the case, one would expect multimodal adaptiveness of luminescence with at least some evidence for a defensive function. Light signals could be used in many ways to reduce predation, but for spontaneous glowing species in particular, aposematism seems the only functional strategy. In a preliminary experiment with glowing and non-glowing dummy prey, we found that wild-caught toads discriminated against glowing prey. They showed significantly lower attack responses and higher latencies towards glowing prey dummies. However, some of the toads were less reluctant because they did not distinguish initially between prey with or without the light stimulus. Since the toads were collected in areas abundant with lampyrid glow-worms, which is the only luminous organism at this locality, and our results concur with the general evidence that they may have had previous experiences with this prey, we attribute the result to luminescent aposematism. From the literature, and from our own experiments, we know that toads and many other potential predators experience lampyrids as disagreeable prey. In future experiments we will test whether glow-worms are defended by luminescent aposematism or not.