European hornet is an intimidating new neighbor

While recently barbecuing on my deck I saw an enormous hornet. It commanded attention because it seemed to be the size of a hummingbird. Everyone present stopped their conversation to watch this insect hover about, hoping that aggression was not on its mind. This was my first good look at a live European hornet.

I have seen numerous dead specimens that the public brings in for identification, and have listened to their descriptions, but I was still surprised to see such a large insect buzzing around the house. This large wasp has recently arrived in Missouri and is becoming more common in the southeastern and central parts of the state.

The European hornet is a native of Europe and Asia and was probably introduced to this country by accident in the 1840s. The hornet was reported in Missouri for the first time around 1984 and can now be found as far north and west as Columbia.

You can positively identify a European hornet by looking for two characteristics. First, European hornets are noticeably larger than other wasps. It is one of the largest wasps in Missouri with an adult length of 3/4 to 1 1/2 inches. The only wasp to come close in size is a cicada killer.

Second, it is predominantly reddish brown to dark brown in color, and a distinct brown "v" can be seen on the upper surface of the thorax or middle part of the body. Some yellow markings are present on the head but the abdomen has the most noticeable yellow.

Night vision

Another oddity that helps identify these stinging insects is their ability to see in low light. They are active at night when other wasps and hornets are dormant. Like many other nocturnal insects, the European hornet is attracted to lights around the home and farm and may fly against window glass or screens. Although it may seem threatening, this behavior is quite harmless.

Unlike the bald-faced hornet, the European hornet typically hides its nest in a hollow tree. It may also be found in attics, sheds, barns, abandoned beehives or in hollow walls or ceilings. A typical nest can be quite large (2 to 3 feet long and 10 to 20 inches in diameter) with six to nine large combs. The combs may be naked, but more often, they are covered by a coarse, papery material fashioned from chewed wood fibers. The exterior is tan or brown rather than gray as with bald-faced hornet nests.

There may be as many as 500 to 1000 workers in a nest at its peak population in late summer and fall, and the nest may have more than one entrance. European hornets dine on spiders, caterpillars, grasshoppers, flies, bees, and other wasps. A large colony can consume a pound or more of insects per day. Other foods of choice are nectar, ripening fruits and plant sap.

When feeding on fruit, the hornet often burrows into and eats the interior, leaving a hollow skin. Hornets eating sap typically girdle or strips bark from twigs, leaving a ragged fringe around a length of exposed wood. The appetite of the European hornet for ripening fruits is often a nuisance to orchard growers and gardeners. The extent of economic damage is not known, but it is probably minor compared to that caused by other pests.

Plants can be harmed

Likewise, damage to ornamental plants caused by the hornet in its search for plant sap can be an annoyance. Although they are not likely to kill lawn and landscape plants, hornets can cause damage or disfigurement.

Although the European hornet is a woodland species, they can find feeding and nesting sites near towns, suburbs, and rural areas. This means frequent contacts with people. Encounters will likely increase as the hornet expands its range and as development in forested areas continues.

Although large, the European hornet is an unobtrusive insect, and because it consumes many insect pests, it can be considered beneficial. However, certain behaviors, like swatting, can appear threatening or annoying to the hornet. As with other wasps, the European hornet can sting repeatedly, and the sting is painful. Normally aggressive, the European hornet will vigorously defend its nest.

The best way to avoid being stung is to avoid fast movement and activity around a nest. If you are stung, consult a first-aid book or a physician for proper treatment.

Out of the house

For the occasional hornet that strays into the home, the simplest action is to let it escape through and open door or window. Hornets may respond aggressively to more active measures, but you can also eliminate the nuisance with a fly swatter or a vacuum cleaner. Household wasp and hornet sprays may not be strong enough to kill European hornets; stronger, long distance knock-down sprays are best.

An active nest in or near the home, garage, barn or shed is another matter and may require fumigation. Keep in mind that a perceived threat to the nest can result in an attack by several hundred angry hornets, all capable of stinging repeatedly.

Destroying an active nest is best left to a pest-control professional.

The European hornet has become -- whether we like it or not -- a permanent part of the landscape. Fortunately, people and hornets can coexist with few conflicts. Gaining an understanding of the European hornet and its behavior is the best way to avoid future problems. That way you will be left with a sense of awe and not a painful sting.

A.J. Hendershott is an outreach and education regional supervisor with the Missouri Department of Conservation.