Wednesday, June 8, 2016
Tale of Two Wasps
BOTTOM: Horntail Wasp Larva
A few days ago a neighbor offered us some free wood, most of which needed to be split. I have never been known to reject free wood, no matter how much work has to be done to get it ready for the fireplace. So, there I was, pounding a star wedge into a chunk of maple with a sledgehammer, when the wood yielded to the efforts and cleaved in two. To my amazement, in one of the larva chambers bisecting the pieces, a Giant Ichneumon wasp emerged. I've seen them in the wild many times, but never encountered one while splitting wood, probably because I usually split wood in the fall as opposed to late spring. I immediately went in the house to grab a camera to document it.
After photographing the wasp, I began to more closely examine the wood, and found that there was an intact Horntail wasp larva still in its chamber, feasting on the wood. The complete developmental cycle of these two very different wasps! The female horntail uses an ovipositor to bore into the wood to insert her egg within, where the growing larva consumes the wood, creating a trail. Meanwhile, the ichneumon wasp uses her antenna to listen for the horntail larva chomping and moving, and when she finds one, uses her even longer ovipositor to pierce the exterior of the wood and inject her egg into the horntail larva, which it then consumes. Clearly the ichneumon is a parasitic wasp, but then so is the horntail.