Spiders discovered using leaf traps to catch prey

Shutterstock.com/ Pong Wira

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Recently, some scientists in Madagascar noticed something odd involving spiders and various leaves on the premises of a vanilla plantation. Said leaves were sewn with spider silk in such a way that pairs of leaves would be stitched along the sides, resulting in an arboreal variant of the sort of trap door mechanism that trap door spiders are known for except that the species of spider responsible for this sort of trap, which seemed to focus on frogs, is a huntsman spider.

The researchers of this recently published study found four structures that had been modified in this unique way, indicating the the huntsman spider intends to use the leaf-traps to snag and secure frogs looking for somewhere cool to hide out. Indeed, the common name “huntsman spider” is indicative of how sometimes this species does not rely on a static web to catch its prey and will instead actively seek our food on their eight feet. One unidentified species of this spider, belonging to the genus “Damastes” seems to lay in wait until one of its traps secures a meal.

Thic Fulgence, co-author of the research, said that his team believes the leaf trap approach is a systemic one. They believe that these traps are made specifically to ensnare frogs; these frogs likely notice the overlapping leaves and head for them as a means of gaining shade from high temperatures and cover from predators.

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Spiders have used silk as a means to catch their prey for more than 400 million years. While we know of over 45,000 different species of these arachnids, not all of them will bother constructing a web despite their innate ability to produce silk through their spinneret organs. Orb-weavers use their silk to make traps, bola spiders turn their silk into a single sticky strand that they swing around like a fascinating lasso and other species of spider have been known too use their silk-weaving skills to build shelter or as a means of restricting the movement of their prey.

Despite all that we know of spiders, only one single instance of this particular species of huntsman spider devouring a frog captured by the leaf traps. Given the rarity of such an approach too feeding, some scientists have wondered if its is merely coincidence that these huntsmen are ensnaring frogs with leaf traps; that the actual situation is that these spiders have been using the leaf rigs as natural shelter and any feasting on frogs is merely out of a sense of territoriality and opportunity.

Jose Valdez, a conservation biologist with Germany’s Center for Integrative Biodiversity Research acknowledges the skepticism of such claims but also admits that sewing leaves together to create a hideaway involves a lot of work. Furthermore, he presents the many other opportunities for hiding spots a huntsman spider could use around the rest of the forest as further evidence that there is something more to the traps than mere refuge. Valdez specifically addresses that not only were the leaf “retreats” discovered on multiple occasions but that every instance of them was clearly tweaked to have its edges woven together with spider silk.

Authors of this particular scientific study wanted to clarify that this story is not the first instance of a spider dining on frogs within the island nation of Madagascar. These researchers hope that their study will serve as a basis to analyzing other forms of vertebrate predation carried out by huntsman spiders.

Sidebar: a bit more on spider silk

Spider silk has long fascinated the various STEM fields due to its many quirks. While spiders have a great deal of control on the types of silk they can produce, individual strands can be thinner than human hair yet bear a tensile strength that exceeds that of a Kevlar vest. Indeed, while Kevlar withstands up to 50 megajoules/meter, spider silk can withstand up to 180 megajoules/meter.

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