Prey size influences the feeding behaviour of predatory female Photuris lugubris fireflies (Coleoptera: Lampyridae)

Hunting female fireflies of the Photurinae subfamily specialize in feeding on heterospecific male fireflies, generally smaller than themselves, responding to their courtship signals. Photuris spp. females hunt males of Photinus spp. species, from which they obtain nutrients and defensive toxins. In some localities, Photuris lugubris is sympatric with Photinus extensus , whose males are larger than the hunting females. Here, we report a field study of the frequency of interactions between signalling P. extensus males and hunting P. lugubris females. We also report an experiment to determine whether P. lugubris females attack and feed on P. extensus males in captivity. In more than 18 h of focal observations, we only observed one case in which a P. extensus male was attracted by a P. lugubris female, but no attack occurred. In our experiment, females attacked in 17% of the opportunities they had. However, instead of the typical feeding on soft tissues and killing of the prey (as observed, for example, when P. lugubris females feed on males of the smaller Photinus palaciosi ), the females restrained the males with their legs and mandibles and fed on the liquid substance (presumably, haemolymph) exuded from pores located along the margin of the elytra and pronotum (reflex bleeding). All attacked males freed themselves and recovered from the attack. To the best of our knowledge, we are the first to report this peculiar non-lethal predatory behaviour in fireflies.