Imma Perfetto
Cosmos science journalist
New evidence suggests an orb-weaving spider, Araneus ventricosus, somehow manipulates male fireflies in its web to mimic the flashing signals used by females to attract mates.
Unsuspecting males pursuing the supposedly free females are then ensnared in the web, luring more males to their deaths in turn.
How the spider is doing it isn’t yet clear, but the researchers suggest it could be the results of a specialised behaviour involving wrapping and biting its prey.
The findings are described in a new paper in the journal Current Biology.
A. ventricosus is a nocturnal species of orb-weaving spider found primarily in China, Japan, and Korea.
In the field, first author of the study Xinhua Fu from Huazhong Agricultural University, China, noticed a strange, skewed pattern in the species’ webs.
They almost exclusively contained male fireflies (Abscondita terminalis), but females were very rarely, if ever, trapped.
Fireflies are known for communicating using stunning flashing signals produced by bioluminescent lanterns on their abdomens.
In the species A. terminalis, these signals differ between males and females. Males make multi-pulse flashes using their 2 lanterns to attract females, whereas females make single-pulse flashes with their single lantern to attract males.
Field experiments revealed the orb-spiders’ webs captured male fireflies more often when the spider was also present on it, compared to when it wasn’t. The trapped male fireflies also produced single-pulse signals using only 1 of their lanterns when the spider was present, but only rarely when it was absent.
The findings suggested the males weren’t altering their flashes as a distress signal. Instead, the researchers propose the spiders alter the fireflies’ signals somehow.
“We propose that in response to seeing the ensnared male fireflies’ bioluminescent signals, the spider deployed a specialised prey handling procedure based on repeated wrap-bite attacks,” the authors write in the paper.
“We also hypothesise that the male firefly’s neurotransmitters may generate a female-like flashing pattern. For determining whether it is the spider’s venom or its act of biting that exerts the manipulating effect on flashing, further research is needed
