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Picture of the Week for 18 October 1999

Bald-faced Hornet Nest

(The following is an article from Down the Garden Path (Issue 86, September 19, 1995), concerning Baldfaced Hornets.)

Bald-faced Hornets -- A menace to society!

Corey Gerber, Insect Diagnostician

Bald-faced hornets, Vespula maculata, are rather large wasps measuring 5/8 to 3/4 inches in length, and are very well known for their painful stings. Also, they have an intricate black and white pattern on their face, thorax, and abdomen. Adults can be found along meadows, forest edges, and around our homes. Diets of the adults consist of nectar, fruit juices, and even small insects.

Overwintered mated females will emerge in the spring and begin to build nests. Baldfaced hornet nests are large, grayish, pear-shaped paper nests. The thick paper material will enclose two or four horizontally arranged combs. These nests are typically suspended in trees, shrubs, or along the side of buildings.

After a female builds a nest, she will lay eggs that will hatch into female workers. The main purpose of these first generation workers is to bring back food for second generation larvae. Larvae diets consist of insects pre-chewed by the adult workers. Once the larvae in the cells have matured, they will seal themselves within these cells for pupation. In late summer, males will emerge from unfertilized eggs and mate with selected females that will overwinter. In late October or early November, males, workers, older queens, and larvae die off.

Often, homeowners will detect baldfaced hornet nests around their yard. Many home insect sprays are not effective against a hornet colony. Before using any pesticide, read and follow label directions. Colonies that are found in the upper canopy of very mature trees (40 to 50 feet high) should be left alone. However, if you are interested in collecting these paper nests, remember that the colony can be active until early November.

Baldfaced hornets are almost always uninvited guests at fall picnics. Hornets are readily attracted to trash cans located around picnic areas. As the hornets sense recently baked apple pie, they will leave the trash cans and become a disturbance near picnic tables. Then, people will begin to swat at the hornets, provoking them to aggressively sting. Ouch, that can hurt! So if you decide to have a fall picnic, try to eat delightful delicacies (apple pie, pumpkin pie, and other savory sensations) away from trash cans and other areas that may be appealing to the hornets. Have a very enjoyable and safe autumn.

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