Female wasps have a long, needle-like organ called an ovipositor, used for piercing plant tissues or the hard exoskeletons of insects, and to lay her eggs.
In 2015, Niclas Fritzén and Ilari Sääksjärvi of the University of Turku, Finland, trekked out into the western part of the country to find some Clistopyga wasps, a species that is little studied and often mistaken for other wasps.
“This species is not easy to collect, and is impossible to study in nature,” says Fritzén. “They need to be collected and reared from the hosts [on which their eggs have been laid] in the lab.” Those hosts are a kind of jumping spider, Salticus cingulatus, which the wasps first paralyse using venom.
The scientists collected a single young female Clistopyga wasp they found on a paralysed jumping spider, along with some pieces of bark with some spider nests. They brought their collection back to the laboratory and began their observations. What they discovered is truly amazing.
The Clistopyga female was offered spiders within their silken nests, and what she did was decidedly an evolutionary adaption. Using her ovipositor, she pierced the spider, injecting her venom, and preventing it from moving. She didn’t kill the spider but paralysed it.
Then using her ovipositor again, she reinserted it into the spider to arrange it into a more favorable position before she laid her eggs. After laying her eggs, she then used the ovipositor to pick up pieces of the silken web and literally sewed the web inside a miniature coffin covering the spider. Once the wasp’s eggs hatch, they will have fresh food.
Describing the sewing motion, Fritzén says, “The needle goes up and down like in a sewing machine. The silken nest of the jumping spider is very soft and fluffy, because they consist of parallel layers of silk, apparently with a lot of air between.” Fritzén added, “Entangling these layers makes the silk more packed and stiffer, apparently also more durable.”
The workmanship is akin to “felting.” And the BBC says no other insects are known to felt like this. Fritzén says, “This is another beautiful textbook case of how a new behaviour has evolved from a structure originally adapted for something completely different.”
This interesting study, “Spider silk felting—functional morphology of the ovipositor tip of Clistopyga sp. (Ichneumonidae) reveals a novel use of the hymenopteran ovipositor,” was published in the Journal Biology Letters on August 9, 2016.
