From the Hymenoptera order of bees, wasps, and ants, the ichneumon wasp comes from a species that is almost all considered parasitic since they develop on or in the bodies of other insects. This has made it difficult to observe their life cycle since the larvae stage is spent on or inside the bodies of their food sources. As for the adult ichneumon wasp, the best way to find it is to watch for a thin, delicate wasp that has antennae that is about half the size of their body.
Occasionally the antennae will have white or yellow segments in the middle. The body will be an orangish-brown and about one inch long or smaller. They can usually be seen around the window screens at night since they are attracted to light or flying about the garden hunting for a host insect such as the cutworm.
The abdomen of the ichneumon wasp long and slightly curved with flattened areas on each side. This wasp appears to be wary around humans although some have been known to fly into houses during the late spring months. Although in most cases the ichneumon wasp is harmless to humans, when trapped with a human hand they have been known to apply a painful sting.
There are over six thousand species of ichneumon wasp in North America, the largest of which is the Megarhyssa macrurus. With a body of up to three inches long and its long ovipositor adding up to four more inches to its length, this insect is quite a fascinating sight. In-flight the ovipositor trials behind this insect appearing as several strands of thread.
The ovipositor of this ichneumon wasp is used to penetrate through the wood so eggs can be laid in the developing larvae of the horntail wasp which is a primitive wasp whose larvae feed in tunnels inside the wood. It is believed this ichneumon can pick up the vibrations the feeding horntail wasp larvae with its sensitive antennae.
The ichneumon eggs develop in the larvae of the horntail wasp, killing them when they are fully grown. They will then pupate inside the tunnel of the horntail, chewing their way out when they reach the adult stage. The females of this species can be seen moving about the bark of trees depositing their eggs while the males stay nearby.
The several different species of the ichneumon wasp are known to parasitize the larvae of tent caterpillars, silk moths, cutworms, tussock moths, fall webworms, butterfly caterpillars and in some cases, even their own species. Each species of this wasp tends to choose one host species to parasitize.
This can be observed by watching the female ichneumon as she hunts over plant life. She will not be feeding but instead moving about feeling with her antennae. Once she finds a particular host she swoops in to lay her eggs. The eggs will hatch in or on the host and the larvae will develop inside the body of the host. In most cases, this does not kill the host insect until the larvae of the ichneumon have completed their development.
This may occur even after the host has transformed into another stage and has been known to take from one to many generations in the period of one year. The best way to observe the parasitic effects of the ichneumon wasp is to look for the remains of a caterpillar or cocoon. If you find small, hard, oval pupal cases inside this is a sign that the