Bug of the Week

Ichneumon Wasp (Family Ichneumonidae)


Hi, BugFans,

First off, this is not Everywasp, the yellow and black gal most people visualize when they hear the word. In fact, there are blue-black mud daubers, metallic green cuckoo wasps, and orangey ichneumons. Wasps belong to the order Hymenoptera (membrane wings), which includes the ants, bees and wasps and a few hangers-on like sawflies and horntails. Some species are social, living communally with strict caste systems, but most are not. Hymenopterans have two membranous wings (royal ants are the only ones that get to fly, just once in their lives).

Ichneumon wasps are frequent visitors to porch lights in early summer.
Ichneumon wasps are frequent visitors to porch lights in early summer.

They tend to have long, jointed antennae and a narrow “waist” connecting the thorax and abdomen. Stingers are modified ovipositers – workers don’t mate, but many species do not sting. Hymenopterans have a “complete metamorphosis,” which means that eggs hatch into larvae that rest as pupae and emerge as adults that do not resemble the preceding stages and may occupy a different habitat, have different kinds of mouthparts and eat a different diet than the larva did. Hymenopterans are considered the “most evolved” insects.

Ichneumon wasps are members of a large and very confusing family with over 3,000 species north of Mexico. It belongs to the subfamily Ophionidae. Ichneumons frequently have a white or yellow band on their antennae and they may be “twitchy.” Their long, often-curved abdomen may be “flattened.” Some ichneumons have impressive-looking “stingers,” which are actually ovipositers (“egg-depositers” to you classical language scholars.). One author reports getting a healthy sting while escorting an Ophion ichneumon from the house manually.

The adults drink nectar and water. Ichneumons lay their eggs on moth or butterfly caterpillars or in the larvae of their distant relatives, the horntails and sawflies. Spiders and other insects may also be hosts. Their parasitic larvae feed internally or externally on their hosts and ultimately emerge as adults from the host’s pupa, (which sounds to the Bug Lady like a magician’s slight-of-hand). The host does not survive. Ichneumons are considered important control of pest insects.

Female Giant Ichneumon wasp (Megarhyssa sp.) lays its eggs on horntail larvae in rotten wood. Male Ichneumon wasp (Megarhyssa sp.)
Female Giant Ichneumon wasp (Megarhyssa sp.) lays its eggs on horntail larvae in rotten wood. Male Ichneumon wasp (Megarhyssa sp.)

One of the Bug Lady’s favorite insects is the Giant Ichneumon Wasp (genus Megarhyssa), a sizable wasp with a sizable (3+ inches) ovipositor that she curls up over her body at rest. A male Megarhyssa, about the size of a damselfly, flew into the BugLady’s car one day and stayed long enough for a portrait. The female lays her eggs in the tunnels made by horntail larvae in the rotten wood deep in a dead tree. She finds the larvae by landing on the tree trunk and laying her antennae against the bark. When she senses the movement of a horntail within, she precision-bores into the chamber, using the sharp tip of the ovipositor, until she can lay an egg on the horntail larva. Her larva lives as an external parasite on the horntail; the full-grown ichneumon larva abandons its dying host and pupates in the tunnel; the adult wasp has to chew its way out.

And, “Ichneumon” comes from the Greek word for “hunter” or “tracker.”

Wowsers!

The Bug Lady