A GIANT WASP LIVES AMONG US

by Whit Gibbons

October 4, 2015

Environmental adventures can await just outside your own door. My wife and I recently had a spectacular wildlife encounter on our front porch. Hanging from the ceiling was the longest wasp found in North America. Half a foot long is big for any insect, but a wasp?

Some people might argue that the stinger of a wasp should not be counted as part of its length. Whichever side you choose, it is a take-it-to-the-bank fact that the creature my wife and I found had a body 2 inches long and a "stinger" that was more than 4. We were looking at a giant ichneumon wasp that was absolutely stunning in appearance.

The actual body of this Goliath of the wasp world was longer than an average paper wasp. Its color was alternating bands of orange, yellow and black. But the feature that would catch anyone's eye was the ovipositor. An ovipositor is simply a tube some animals, notably insects, use to lay eggs. An ovipositor doubles as a stinger in many kinds of wasps, bees, and hornets. The ovipositor of the giant ichneumon wasp can be almost 5 inches long! Imagine a wasp with what appears to be a stinger long enough to go through your arm.

Sometimes, however, an ovipositor is just an ovipositor, serving the purpose of transmitting an egg from the female's body to the location where she wants it to hatch but not being used as a stinger. This is the case for this largest of the large ichneumon wasps. Some smaller ichneumon wasps can sting, as I have learned by picking one up to find out.

All ichneumon wasps have a pretty amazing lifestyle, which for most involves laying their eggs in or right next to another insect or a spider. When the egg hatches, the wasp larvae feed on their unfortunate host. In the case of smaller ichneumon wasps, the host animal may be temporarily or permanently paralyzed through stinging.

For the giant ichneumon wasp, the victim is the larva of another species of wasp called a pigeon horntail or wood wasp. The whole life cycle relationship between giant ichneumon wasps and pigeon horntails is extraordinary - and not to the advantage of the wood wasp. They are also large wasps that do not sting. They use a long ovipositor to bore into the wood of a dying tree and deposit eggs. The larva of a wood wasp eventually hatches out and chews its way to the surface. However, female ichneumon wasps have another plan for wood wasp larvae as they rest peacefully inside a tree.

The female ichneumon wasp lands on a tree and uses her long antennae to feel along the surface to detect vibrations that indicate a wood wasp larva is inside. Then she inserts her incredibly long ovipositor by pushing or drilling several inches into the tree until she locates the wood wasp larva and deposits her egg next to it. When the giant ichneumon larva hatches out, it begins to devour the helpless wood wasp larva and later emerges from inside the tree as a full-grown giant ichneumon wasp.

Upon appearing on the surface a female giant ichneumon is usually greeted by several male suitors, one of whom successfully mates with the female who then goes about her egg-laying mission. Her diet plan for maintaining a wasp waist is basic enough - don't eat, just lay eggs and die. We don't know if the one on our porch was in the process of looking for egg-laying sites or had already completed her task, but as we watched the big insect fly away into the yard, my wife said, "Between us we've lived well over a century. How could we both have missed something that remarkable?"

Wildlife adventures may not greet you every day the moment you walk out the door, but you shouldn't have to look far to find something in yard, park or local woods that you've never before seen.

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