Prey bioluminescence-mediated visual luring in a sit and wait predator.

As behavioural and physiological processes can be costly for animals to employ, deception and other dishonest strategies may become necessary for sit-and-wait predators. Sheet-web spiders Psechrus clavis have been known to use their body colour and webs as visual cues to deceptively lure and immediately consume lepidopteran insects. However, they do not immediately consume trapped male fireflies Diaphanes lampyroides; instead, the spiders retain them in their webs while the fireflies continue to emit their bioluminescent signal for up to an hour. This observation raises the question: can the spiders exploit prey signals to attract additional prey, thereby enhancing their foraging success? We hypothesized that such a unique prey-handling strategy serves to enhance P. clavis' foraging productivity by exploiting the prey's own signal as a deceptive lure. To test this hypothesis, we performed a field manipulative study using light emitting diodes (LEDs) resembling the bioluminescent signal of D. lampyroides and evaluated the responses of fireflies and other prey using infrared video cameras. We found that the presence of the simulated firefly signal significantly increased prey attraction and interception rates within P. clavis webs. We also found male D. lampyroides to comprise the bulk of the additional prey obtained. We speculate that this enhanced foraging return allows P. clavis to reduce its energetic and nutritional investment in insect-attracting body coloration. This study sheds new light on the ways that nocturnal sit-and-wait predators can rise to the challenges of attracting prey and provides a unique perspective on the complexity of predator-prey interactions.