Spiders seen keeping fireflies as glowing prisoners that draw more prey to their webs

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The fireflies are kept inside the webs for as long as they glow, before being consumed.

Nocturnal spiders have been filmed capturing fireflies and keeping them in their webs to attract more prey, even intermittently checking on them over the course of an hour, according to a new study.

sheet web spider with leaves behind

Nocturnal sheet web spiders utilize the glow of fireflies to attract more prey to their webs, scientists discover. (Image credit: Davy Falkner)

"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," Tso added.

The researchers had noticed sheet web spiders (Psechrus clavis) — which build their sheet-like webs close to the ground — had accumulated a number of winter fireflies (Diaphanes lampyroides), and thought these glowing bugs may have been used as a visual lure. To find out, the team developed a series of field experiments, placing LED lights resembling fireflies and sheet spider webs, and left other webs empty as controls.

Related: Diving bell spider: The only aquatic arachnid that creates a web underwater to live in

The findings, published Thursday (Aug. 28) in the Journal of Animal Ecology, revealed the LED webs attracted three times more prey than the empty webs. When just looking at the number of fireflies caught, the LED webs snared 10 times more than the non-LED webs.

a glowing firefly caught in a spider web

A firefly glowing from the confines of spider's web, where it is being used as bait to attract more prey. (Image credit: Davy Falkner)

Sheet web spiders, found in subtropical forests of East Asia, normally sit in the dark, waiting for prey to approach. Footage captured by the researchers shows that if another insect, such as a moth, is caught, the spiders eat it immediately. But the fireflies were left for up to an hour before being consumed, which is about the same amount of time that a female firefly emits a glow in a fixed location, the authors wrote in the study.

Most of the captured fireflies were male, which the authors say may indicate males mistook the stationary glow for potential mates.

The researchers think the spiders — unlike other sit-and-wait predators that have developed their own bioluminescence, like anglerfish — have worked out how to exploit fireflies' sexual cues to their advantage.

"Handling prey in different ways suggests that the spider can use some kind of cue to distinguish between the prey species they capture and determine an appropriate response," Tso said. "We speculate that it is probably the bioluminescent signals of the fireflies that are used to identify fireflies enabling spiders to adjust their prey handling behavior accordingly."

Spider quiz: Test your web of knowledge

Hannah Osborne
Hannah Osborne
Editor

Hannah Osborne is the planet Earth and animals editor at Live Science. Prior to Live Science, she worked for several years at Newsweek as the science editor. Before this she was science editor at International Business Times U.K. Hannah holds a master's in journalism from Goldsmith's, University of London.

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