Yellow jacket. Photo credit: John Obermeyer/Purdue Entomology
Yellow jacket. Photo credit: John Obermeyer/Purdue Entomology

We are approaching the time of the year in the Midwest when a warning to the wise is "The Yellow Jackets are coming!" Yes, it is during the months of August and September when encounters with these stinging insects grow in abundance.

Yellow jackets are a type of wasp known as social vespids. These wasps are called social because they live in colonies consisting of three forms of individuals: queens, workers and drones. The name vespid is based on the Latin word for wasp. That word is used in both the family name (vespidae) and the genus name (Vespula) for this group of insects.

These social vespids chew up wood as raw material from which they construct nests. Consequently, the vespids are also known as paper wasps.

Paper wasps are also known for their stinging ability. The female workers possess a stinger and are not hesitant to use that weapon in defense of themselves or their nest. Historical entomologist John Henry Comstock puts it this way in his 1895 book, A Manual of the Study of Insects: "Any person who has no respect for the rights of yellow-jackets has before him a lesson which he will have no difficulty in learning, if he takes the pains to disturb one of the oval, gray paper nests commonly found hanging from the eaves of buildings. The yellow and black mass of seething and buzzing vengeance that can pour out of the hole in the bottom of one of these nests seems almost as wonderful as the miraculous multiplication of the loaves and fishes. And these insects do not threaten more than they can perform: their painful stings are so well known, that neither man nor beast trespasses willingly on their domains."

In general, yellow jackets have been described as void nesters. That means they build their paper nests in voids such as in old rodent nests in the ground or even in an enclosed attic space. However, sometimes insects called yellow jackets will build an exposed nest under the eve of a building. Such behavior is associated with an introduced species of vespid known as the German yellow jacket.

Also to confuse the issue is the fact that the insect known as a bald-face hornet is technically a vespid. Bald-face hornets build their nests outside, suspended from the limb of a tree. Or occasionally the nest is attached to the siding of a structure. Even though the bald-face hornet has hornet in its name, it is not classified with other hornets but with the yellow jackets.

So this time of year, regardless of the specific species or nest location, the vespid colonies are populated with numerous individuals. That is why you can sometimes "stir up a hornets' nest" without really trying.

One of the sure ways to raise the ire of the inhabitants of a paper nest is to run over the area with a power mower. This is the way some people discover a yellow jacket nest they did not even know existed.

That happened to me last week. I was cleaning up some overgrown pasture with a hand-driven brush cutter when I noticed a group of dark insects zooming around the ground over the area I had just mowed. But the insects did not appear to be yellow jackets, even though they were coming from the ground. So I decided to retrieve my trusty, old insect net from the garage to collect a few for a closer look. By the time I got back to the location no insects were visible. At least that was the case until I poked the ground with the handle of my insect net. The result was predictable. A number of the insects roared from the debris. I quickly captured a few with my net and retreated from the scene. But not quick enough! I got stung.

As it turns out, the insects were bald-face hornets, and they are not supposed to nest underground. However, further investigation showed that the nest was located in the soil. So I encountered what apparently is an unusual situation - bald-face hornets rather than yellow jackets nesting in the ground. And if you don't believe me, I have the insects and a sting to prove it!

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