Watchful Tolerance Best Policy for These Hornets

The latest wave of European immigrants to invade Missouri may upset some people, but scientists say European Hornets actually benefit the ecosystem.

The European Hornet is the largest of the vespid wasps in North America, growing to 1.5 inches. Vespid wasps live in colonies. The European Hornet is the only wasp that is brown with yellow markings, says Richard Houseman, entomologist at the University of Missouri-Columbia.

Staff at the University Outreach and Extension Office in West Plains received more than a dozen calls last month from residents alarmed about--and stung by--these hornets.

Colonies are typically largest and most active in late summer. While hornets normally don’t sting unless provoked, they will defend their colonies, Houseman said.

European Hornets arrived in New York around 1840 and now are found throughout the eastern United States and Canada.

They prefer forested areas. Their nests are usually paper-like combs that are brown, distinguished from the gray nests of Baldfaced hornets.

“They came over on a ship in the 1800s and have been migrating west for years,” said Randy Saner of the Extension Office. “They are big and exotic looking, and we have received more calls this summer from concerned people than we ever have.”

Saner suspects the reason is increased construction in forest areas.

“I have a feeling these hornets have been around here for years,” he said. “But since we have seen an explosion of new homes and construction in the country, there has been more human contact with them than ever.”

European hornets are actually beneficial insects, says Houseman. They prey on caterpillars, grasshoppers, flies and other wasps.

But they also attack honeybees and will eat ripening fruit. The large wasps can also damage landscape trees and shrubs, chewing the bark from twigs to find sap.

Houseman recommends that the hornets not be exterminated unless absolutely necessary. If they must be controlled, the nest must be destroyed--something best left to professionals.

For do-it-yourselfers, Houseman recommends working after dark when the wasps are in the nest, using veils and a flashlight with red cellophane over the lens. Chemical products, called wasp freezes, can also be used to send a pressurized stream of insecticide into the nest opening from 15 feet away.

Large colonies may number 1,000 in summer. However, all except the newly formed queens die at the start of winter. These queens build small nests and start new colonies the following year.