New parasitic wasp may use built-in saw to escape from its hosts

February 2, 2018, 12:15 p.m.
Parasitic wasp Dendrocerus scutellaris on display
Photo: Carolyn Trietsch

A newly named and described wasp the size of a sesame seed is the stuff of nightmares.

The wasp, officially Dendrocerus scutellaris, has spiny ridges along its back that scientists think it uses to literally saw its way out of its host after birth.

This jagged feature along the wasp's back, called a mesoscutellar comb, is visible near the top of the photo above.

Parasitic insects lay their eggs one of two ways. They either deposit them near or on a host so that the hatched larvae can feed on the host from the outside, or they lay their eggs inside the hosts and the larvae eventually eat their way out of the host.

Most of these second kind of wasps, called endoparasitoids, have jagged teeth which they use to chew their way out of the host. But based on their spiky backs, researchers suggest that Dendrocerus scutellaris may rub those spikes against the interior of the host until it can burst out, like a xenomorph from someone's chest in the film "Alien," making it an endoparasitoid.

We haven't observed this behavior in the wild, however. The researchers are basing their work on observations made from samples collected in 1985. Their study is published in Biodiversity Data Journal.

But don't judge this host-sawing wasp too harshly.

"While their lives may sound gruesome, parasitoid wasps are harmless to humans and can even be helpful," the scientists said in a statement. "Depending on the host they parasitize, parasitoids can benefit agriculture by controlling pest insects like aphids that damage crops."

As for its branching antenna, extending from the bottom of the wasp's head in this image, the researchers think it could be used to sense mates or potential hosts.

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