Research shows that certain spider species can manipulate the light signals of male fireflies caught in their webs to mimic the “mating call of females.”
Spiders have evolved an impressive array of hunting techniques – from trapping prey with silk to creating “sheets” strong enough to catch snakes. Researchers have discovered a particularly toxic strategy that some “web-weaving” spiders can employ to lure fireflies into their webs.
A study published in the journal Current Biology reveals that some spider species seem to control the flashing signals of male fireflies ensnared in their webs to imitate the signals of females.
This shimmering “love call” attracts other male fireflies to the spider’s web, much like a siren’s song leads sailors to their doom.
Researchers believe that spiders may manipulate the bioluminescent signals that fireflies use to find mates. (Source: National Geographic)
Dinesh Rao, a researcher at the Veracruzana University, stated that the idea of spiders delaying their meal and using prey as bait is inherently fascinating.
“Spiders are always hungry, right? – So to say, ‘Okay, I won’t eat this firefly right now, and I will wait for the next one,’ is quite intriguing.”
However, while Rao and other experts agree that something is altering the flashing pattern of the trapped male fireflies, they have stated that further research is needed to determine whether the spiders are indeed “behind this action” and how they accomplish it.
“The Deadly Love Call”
While observing spider webs in the fields in 2004 during her doctoral research, Xinhua Fu, a firefly researcher from Huazhong Agricultural University in China and the lead author of the study, noticed something unusual: Only male fireflies became ensnared in the spider’s “deadly” trap. Oddly enough, some of the trapped males also emitted flashing signals similar to those of females.
Could the spiders be related to this phenomenon?
To investigate, Fu and her team went to a village near Wuhan (China), in an agricultural area dotted with rice fields and ponds. There, they chose to study Araneus ventricosus – a common “web-weaving” spider: Each evening, this spider would “weave” a new web while fireflies were also active.
The research team captured male fireflies and placed them on the spider’s web using small tweezers. They then set up cameras to observe what happened in different scenarios.
“When a male firefly gets caught in the web, the spider first wraps the firefly tightly and then bites into its chest, injecting a small amount of venom,” Fu explained. After that, the spider leaves the male firefly in the center of the web and hides at the edge of the web.
Before long, the trapped firefly begins to produce flashing signals similar to those of females – including single pulse flashes – attracting other male fireflies searching for mates to the spider’s web.
When the firefly stops flashing, the spider repeats the process. Fu stated that the entire process typically lasts about two hours, after which the spider begins to consume its prey.
Fu noted that the research team was surprised by this behavior since web spiders are known to have poor eyesight. Nevertheless, it seems that they “can still detect flashing patterns with varying intensities.”
Need for More Evidence
But what exactly causes the flashing signals of fireflies to change?
Fu and her research team hypothesize that the spiders are somehow manipulating the flashing signals of the fireflies – they speculate that it could be through their venom. However, more evidence is needed to support this hypothesis.
Spiders are known to use mimicking and deceptive signals to catch prey. (Source: National Geographic)
“Overall, the paper is very interesting,” Rao commented. “The only thing I’m not completely convinced about is whether the spiders are actually doing something to change the flashing patterns of male fireflies.” He noted that a neurological study is needed to understand precisely what causes this change.
Kathryn M. Nagel, a Ph.D. candidate specializing in spider behavior at the University of California, Berkeley, agrees with Rao. She believes “more research is needed to determine whether the spiders are directly ‘manipulating’ the signaling behavior of the fireflies.”
Fu indicated that the next step for her and her team is to research “how the venom of web spiders affects the ability to control firefly luminescence.”
Spiders are known to use mimicking and deceptive signals to catch prey. For example, some spider species hunt other spiders, using “web signals to mimic captured prey to lure the ‘target’ spider closer.” Nagel explained.
Nagel added: “Arthropods are often considered ‘simple’ creatures lacking sophisticated behaviors, but that’s not true.”
“This study and similar research highlight how previously ‘underestimated’ creatures can perform complex behaviors, and there is still much to learn about spider behavior,” she said.
