Fruit fly covered with capture threads of the feather-legged lace weaver (Uloborus plumipes).HANA ADAMOVAThe woolly webs of orb-weaver spiders form an inescapable trap around prey. But it’s not just the threads’ tangles that ensnare meals. As researchers reported this week (May 31) in Proceedings of the Royal Society B, the waxy coating on some insects teams up with fibers from the spider web to form a composite adhesive material, gluing prey in place. Thus, in a rather dark turn of events, the insect’s cuticle promotes its own capture.
Orb-weaver spiders produce fine threads made of nanofibers, arranged like beads on a string with puffs and intermediate zones. The spiders have an organ called a cribellum, which pushes out silk strands, and rows of leg bristles that comb out the silk to produce a woolly texture.
“Cribellar threads are the most primitive form of adhesive capture threads spun by spiders,” says Brent Opell, a biologist at Virginia Tech who was not involved in the study, in an email to The Scientist. “However, this study shows that cribellar thread can implement an even greater range of adhesive mechanisms than previously thought.”
Kukulcania hibernalisFLICKR, MARSHAL HEDINUnlike other types of spiders that produce viscous silk, orb-weavers were not known to make any type of glue, yet prey appeared to get stuck in their webs for longer than in viscid webs. According to the study, scientists had supposed that intermolecular forces, such as van der Waal’s forces that help geckos walk on walls, were at play. But, these forces could not explain the efficacy with which orb-weaver webs ensnared prey.
