Orb-weaver spiders are found nearly everywhere on Earth. They constitute one of the largest spider families (Araneidae), with over 3,100 species. Chances are, many of the typical wheel-shaped spiderwebs you’ve seen in forests, fields, or even your own backyard were made by orb weavers.
With such a thriving population located all around the globe, it’s no surprise that orb-weaver spiders are highly accomplished when it comes to catching prey. Recently, researchers in China discovered that orb-weaver spiders are even more cunning than previously thought. They may have the ability to manipulate the pattern of light pulses emitted by the fireflies caught in their webs in order to attract additional prey.
In a study published this month in the journal Current Biology, a team from Huazhong Agricultural University found that male Abscondita terminalis fireflies caught in the webs of orb-weaver spiders appear to change their flashing patterns to mimic the mate-signalling light flashes usually emitted by female fireflies. Rather than emitting multiple pulses from two lanterns, females emit single pulses from just one lantern. This unusual mimicking behavior resulted in the spiders catching more male fireflies in their webs, as they were presumably duped by the enticing prospect of mating with a female firefly.
To find out how orb-weaver spiders manage to catch so many male fireflies, the researchers placed captured males in 161 orb-weaver webs. They then tested the effects of blacking out the fireflies’ lanterns versus allowing them to flash. They also recorded how many fireflies were captured when the spider was present on the web versus when it was absent.
Caught in a web:
- The most successful combination was a web with a spider present and the male fireflies emitting visible flashing signals. The researchers noted that the males only switched their flashing pattern to resemble the female pattern in the presence of a spider, suggesting that the spider was somehow influencing them.
- Another interesting finding was how differently the spiders dealt with the captured male fireflies compared to non-flashing prey. While other beetles were wrapped thickly in silk and eaten almost immediately, the male fireflies were lightly wrapped so that their lanterns were still visible and could presumably serve as decoys.
- The researchers aren’t sure how the spiders are influencing the flashing behavior, but it could be an effect of the spider’s venom or the bite itself, which could interfere with normal flashing by disrupting the oxygen supply to the lantern. Other scientists say more evidence is needed to prove that the spiders are responsible for the female-like flashing patterns.
