SEPTEMBER
2001

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

9-27-01

A Stinger to Remember

Most people are cautious around insects that possess stingers. And for good reason. Insects sometimes use their stingers to protect themselves and their nests.

But not all insects with stingers will use their poison darts on humans. Many stinging insects use their stingers only to immobilize prey. Scientists call these insects offensive stingers. They sting for food! These are the insects that we know as parasites and predators. Most are wasps, and they paralyze their prey before laying an egg on it.

Mud daubers fit into this category of insects. In general, these black-and-purple colored wasps make their nests of mud. That's the basis for their name. Mud daubers feed spiders to their offspring. Before placing them in the mud nest, the wasps sting and paralyze spiders. That keeps the spiders fresh until the baby wasps make a meal of them.

While the paralyzing wasps seldom sting, some look scary. One such wasp is known as the cicada killer. This is the largest wasp in North America and approaches 2 inches in length. This black and yellow wasp lives in the ground. It catches and stings cicadas, which it places in the ground before laying an egg.

The cicada killer creates concern on the part of some people because of its size. It also has the habit of being territorial. The wasp will hover in a threatening manner in front of humans who come in the vicinity of the nest. Most of the time, it is the male that threatens. In this case, it is just a threat since the male can't sting! At that point, though, most people aren't into deciding if the wasp is a male or female and retreat. Which is what the wasp wanted to happen.

To most people, the most spectacular--and most frightening--of the wasps is the one with the longest stinger. In the United States, this is a wasp called an ichneumon. The insect belongs to a family of wasps called Ichneumonidae.

The wasps, known as ichneumons, have a name based on the so-called Egyptian Ichneumon or Pharaoh's rat. The rat devours the eggs and young of the crocodile and was held sacred by the ancient Egyptians. The name reflects the parasitic habits of this insect. These insects have been called flies. However, they are not flies; they are wasps.

Ichneumon wasps are parasites of caterpillars. There are more than 4,000 species of Ichneumons, and they are distributed across all parts of the United States. These wasps parasitize all kinds of caterpillars, including some very important pest species like the armyworm and tent caterpillar.

One easily noticed characteristic of the ichneumon wasps is that they possess a long ovipositor that is permanently exposed. This is unlike other bees and wasps that hide their stingers until they want to use them.

Stingers of ichneumon wasps are often longer than the wasp itself. This produces a fearsome looking stinger. Fearsome, but worthless, as far as stinging humans is concerned.

The largest ichneumons in the United States are parasites on wood-boring insects, such as horntails, wood wasps and beetles. The long ovipositor is used to drill into wood. Sometimes, the ovipositor extends through an inch or more of wood before an egg is laid in the tunnel of the host insect--quite a feat for the hair-like ovipositor.

So the next time you see a wasp with its ovipositor trailing behind it, remember that its needle is worse than its sting!

 

Writer: Tom Turpin
Editor: Olivia Maddox