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Wednesday, October 21, 2015

Hornets, Feared yet Fascinating

My dogs have brought me some interesting gifts over the years, but when our Marley came up from the field with a hornet nest in his mouth it got my attention pretty quick. By late October, the bee activity is slowing down and since he didn't look any worse for wear, perhaps he didn't pay a price for disturbing the nest. Below is what was left of it, and I have to admit, its construction is pretty interesting. It looked like several paper wasp nests stacked upon one another. The outer covering was missing which is a protection that the nests of paper wasps don't have.

There was one solitary wasp still in one of the cells. From the looks of it, it appears to be a bald-faced hornet. In the picture below it is in the center, a bit to the right. Just the back end is showing.

Bald-faced Hornet
Dolichovespula maculata
cosmopolitan family Vespidae

There is confusion when identifying these insects. The only species of a true hornet in the United States is the European or brown hornet (Vespa crabro). The insect that is really a wasp, but usually thought of as a hornet, is the bald-faced hornet (Dolichovespula maculata). The bald-faced hornet is actually a yellow jacket. All of the yellow jackets in the genus Dolichovespula build nests in bushes, trees and sides of buildings, and produce the grey papery nests.

The insect we usually think of when we say yellow jackets build both above and below ground nests, underground more often. Other differences include:
Hornets are 1 - 1 1/2 inches long, whereas yellow jackets are an inch or smaller.
Hornet nests can have 100 to 500 workers, while yellow jacket nests can have up to 5000 workers.
Hornets are black and white, jellow jackets are a variety of coloration.
Hornets feed on other insects and are not attracted by sweets, yellow jackets prey on insects too but are scavengers and like sweets.
Hornets are very aggressive and will sting over and over, but usually do so only if the nest is bothered or they are provoked.
Yellow jackets are also very aggressive, but paper wasps are not likely to sting unless threatened.

Paper wasp

Yellow jacket

The Bald-faced hornets have an interesting life cycle. All the workers die off by November, except for the fertilized queens. In the spring, queens that have overwintered in areas of protection such as hollow trees and rock piles, become active and begin to build a nest. She collects cellulose from rotting wood, chews the wood and by adding her saliva, she makes a paste. With that paste she makes a papery material to construct the nest, starting with the stem and enough brood cells to begin egg laying. She feeds the hatching larvae and these young will take over the duties of nest building, food collection, feeding the larvae and protecting the nest. The queen then never leaves the nest and her purpose is to lay eggs. As the colony grows there may be from 100 to 400 workers.

The chosen spots for the nest can be a few feet off the ground in shrubs or way up in the trees. They are a grey color and can reach two feet in height and a foot across. There have been several occasions where towards the end of the summer season and the leaves are starting to die back, I'll suddenly notice a huge nest in an area I've been mowing past or working around without incident all summer long. A little unsettling to think what could've happened had they felt threatened.

Bald-faced hornets can be considered a beneficial insect in that they feed on insect proteins, therefore reducing the populations of unwanted insects.
As the season progresses and there are fewer larvae to feed, the workers will take nectar, so do help with pollination.
With the arrival of fall and the first hard frost, all the workers die off except for the fertilized queens that will leave the nest and seek protection for the winter. The nests are not reused the following spring.

It is wise to have the utmost respect for hornets and unless the nest is in an area where there is a good chance of disturbing them, it is best to just leave them alone. Here is a good post about the subject of whether or not to destroy hornet nests. The good information is in the comment section.

If you do discover a hornet or wasp nest there are a few ways to handle them. Since the workers will die off with the arrival of the cold season, if it is already near fall, try to just use caution around the nest and leave it alone. If the nest is high up in the trees, there is little chance it would become a threat anyway.

If the decision is to remove the nest there are options:
Commercial sprays can be used to kill them. If you choose this route and try to do it yourself, wait until evening when the wasps are all back in the nest and are quiet. Follow the instructions on the can. If over the next few days you still see activity, you may need to repeat the application.

A way to get rid of the nest without using chemicals is to wait until evening and very slowly and carefully cover the nest with a plastic bag. Leave as little opening at the top as possible and cut the branch holding the nest. Moving slowly, relocate the nest to an out of the way area or to kill them, place the bag in the freezer or lay it in the hot sun. They'll die within a day or two.

Information for this post came from:
Penn State College of Agricultural Sciences Extension Office