Spider uses bioluminescence from fireflies as bait to capture new prey

Researchers discovered that the spider Araneus ventricosus, known for spinning orb webs, uses a deceptively sophisticated form of communication to capture its prey, especially male fireflies of the species Abscondita terminalis. The behavior was revealed through a study that investigated how spiders manipulate the bioluminescent signals emitted by fireflies already trapped in their webs, transforming them into live bait to attract more prey.

While most predators actively move in search of their prey, Araneus ventricosus adopted a more passive and resourceful approach. It takes advantage of the bioluminescence of male fireflies, which normally emit light signals to attract females during mating. When trapped in the spider's web, these captured males begin to emit light signals that resemble those of females, attracting other males to the same trap.

The researchers carried out field experiments using a 2x2 design, which involved the presence or absence of the spider in the web and whether or not the captured male fireflies emitted light signals. The results showed that the capture rate of free male fireflies was significantly higher when there were visible light signals emitted by already captured fireflies in the presence of a spider.

Detailed analysis of the signals emitted by captured fireflies revealed that, in the presence of a spider, these males modify their light emission patterns, using only one flashlight instead of two and emitting single pulse signals, which are more characteristic of the signals emitted by fireflies. females. This suggests that the spider, possibly through its bites, is able to manipulate the fireflies' neurotransmitters, causing them to emulate typical female signals and thus attract more males to the web.

The study also ruled out the hypothesis that these modified signals were merely signs of distress or warning flashes between males. The data showed that free-ranging males were more often attracted to webs that contained captured spiders and fireflies compared to webs that contained only fireflies.

The researchers observed that the spider adopted a specific behavior when dealing with captured male fireflies that were still emitting light. 81,8% of the time, the spider performed a sequence of biting and coiling attacks at regular intervals, while the fireflies continued to emit light even during the attack.

The study reveals a sophisticated form of interspecies communication, where the spider Araneus ventricosus uses light signals from its prey to deceive and capture more fireflies. The findings suggest that the spider's venom or bites may be altering the signaling patterns of captured fireflies, turning them into bait that tricks other males.

This research opens new perspectives on how predators can use signals from their prey to improve their hunting strategies, demonstrating a previously underestimated complexity in predator-prey interactions. Further studies will be needed to fully understand the neurobiological mechanisms behind this signal manipulation.

More information on doi.org/10.1016/j.cub.2024.07.011