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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

What is that giant hornet and why is it eating my tree? European hornet, Vespa crabro


Fallen fruit are a favored source of nutrients for many stinging insects. Please don’t go barefoot near fruit trees in autumn lest you have a zesty surprise.


Gangs of European hornets often strip bark from thin-barked trees and shrubs in autumn.

Over the last week or two, I have heard strange reports of giant yellow jacket-like wasps attacking trees and shrubs. A quick visit to one of my victimized neighbors revealed magnificent European hornets stripping the bark from a lilac and greedily lapping exudates leaking from the wound. To construct their supersized paper nest, European hornets strip bark from several types of trees and shrubs including lilac, rhododendron, and birch. This annoying behavior provides the material for making paper and allows them to feed on the nutritious sap and plant tissues beneath the bark. Unfortunately, small plants may be severely damaged by this bark stripping.

European hornets first appeared in the United States in New York sometime between 1840 and 1860.These marvels spread and now occupy territory from the east coast to the Mississippi. In nature these giants use a cavity in a tree for constructing a nest, but occasionally, as was the case with another neighbor, hornets will nest in the wall void of a home or barn. The colony is founded by a single queen that survives the harsh winter beneath the bark of a fallen log or in a similar protected location. In spring when warmer temperatures return, she becomes active, gathering bark from trees, constructing a small paper nest, and laying eggs destined to become workers. After the queen successfully raises her first batch of sterile female workers, she remains in the nest producing brood while her daughters take up the tasks of enlarging the nest, protecting it, and gathering food for the young. Caterpillars, flies, grasshoppers and other stinging insects like yellow jackets are all on the menu. In addition to eating other insects, they feast on fallen fruit. Remember, in autumn many stinging insects feast on fallen fruit. To reduce chances of a sting by a European hornet, yellow jacket, or wasp, carefully pick up fallen fruit and compost it. Wear shoes rather than going barefoot when you walk near fruit trees.



Issuing forth from their nest in a tree cavity, European hornets take wing to search for food.

European hornets are somewhat unique in their foraging behaviors in that they hunt at night. They are also attracted to light and can be found buzzing around porch lights or heard crashing into windowpanes after dark. During autumn, the colony operates at a fevered pace. Inside the colony, the queen no longer produces sterile daughters. She has shifted production from workers to female and male hornets capable of reproducing. Females are destined to become queens of future generations. Males have just one purpose and that is to mate with the new queens. After fulfilling this biological imperative, males die. As autumn wanes, the colony is abandoned and queens find protected places to spend the chilly months of late autumn and winter. The nest will not be reused in subsequent years.

This large nest came from a wall void in my neighbor’s home.

Although these hornets are large and scary looking, humans are unlikely to be stung by European hornets. I photographed these hornets at a very close range and other than receiving an inquisitive stare, I was unmolested. To avoid being stung, simply avoid disturbing the nest site or the hornets. If European hornets have nested in a home or another location that poses a threat to human health or safety, they may be exterminated. Assistance from a professional may not be a bad idea. However, if the nest is out of harm’s way, I favor the approach of my neighbors who had a “live and let live arrangement” with these giants that had taken up residence in a wall void of their home. They decided to give the nest a respectable berth and simply enjoy the comings and goings of these spectacular insects.



Bark removed from a tree provides building material for the paper nest.  Sweet carbohydrates just beneath the bark are apparently a special treat for European hornets in autumn.


Special thanks to Howard Bernstein for alerting me to the hornets in his trees and for sharing a nice image, and to Brooke and Ruth Ann for sharing their ginormous hornet’s nest for this Bug of the Week.