Spiders manipulate and exploit bioluminescent signals of fireflies

Predators often search for prey while moving through the environment, but there are important exceptions, including the way sedentary predators sometimes rely on signals for drawing prey to within striking distance. Some spiders, for instance, leave the remnants of previously-captured prey in their webs where they function as static lures that effectively attract a diverse array of additional prey [1,2,3,4]. Important questions remain concerning how specific targeted prey may be and to what extent the predator’s signals may be made dynamic instead of static. With these questions as our rationale, we initiated research in which the predator is Araneus ventricosus (L. Koch, 1878), an orb-weaving spider, and the prey are the males of a firefly species (Abscondita terminalis) (Figure 1A, B, C). Using two lanterns situated on their abdomen (Figure 1D, F), A. terminalis males make female-attracting multi-pulse flash trains (Figure 1J), but sedentary females attract males by using a single lantern (Figure 1E, G) to make single-pulse signals (Figure 1C, K). Drawing from extensive field observations, we propose that the spider practices deceptive interspecific communication by first ensnaring firefly males in its web and then predisposing entrapped male fireflies to produce bioluminescent signals that deviate from female-attracting signals typically made by males and instead mimic the male-attracting signals typically made by females. The outcome is that the broadcasted false signals attract more male fireflies into the web.