The Giant Ichneumon Wasp

October 2, 2017 at 10:30 am
By Alex Bynum '18

Gian Ichneumon WaspHonestly, I don’t do wasps. What I mean is that I don’t particularly like them and, judging by our many painful encounters, they don’t particularly like me. Suffice it to say, I wasn’t thrilled to be told that we were going to go looking for wasps and other large insects on our Arboretum walk last Friday. Even I must admit, however, that what we found was pretty incredible.

We only walked for a few hundred yards before finding a wasp right on the sandy trail. It was black, only a little bigger than a housefly, and was buzzing around a motionless spider. Scott King, a local wasp and dragonfly expert, explained that the wasp had paralyzed the spider. Now it was dragging it back towards its burrow so that it could lay eggs to hatch inside and later consume the spider. Arguably the most fascinating aspect of this predator-prey relationship is that the spider is kept alive for as long as possible. The larvae will consume non-vital organs first, preserving the spider from rotting by preventing its death. This is a grim death for the spider, but it is a pretty incredible relationship for entomologists to study.

This wasn’t the only egg-laying monstrosity we found that day. An enormous wasp called the Giant Ichneumon Wasp - which is about as long as my index finger - was drilling into tree bark to try and lay eggs on the larvae of another bark-dwelling wasp. In a similar life cycle to our friend the spider paralyzer, its larvae will consume the host while trying to keep it alive as long as possible. We call animals exhibiting this behavior parasitoids. They are an important, albeit creepy, population control.

Wasps come in many shapes and sizes, and they aren’t all aggressive stingers trying to defend their nests. Sometimes they are just trying to eat their hosts’ bodies from the inside out.

-Alex Bynum ‘18, for the Cole Student Naturalists
Photo courtesy of Scott King.

 

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