Forest Preserve District of Cook County, Illinois
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Hornets, Wasps and Yellow Jackets
Nature Bulletin No. 467-A   OPctober 21, 1972
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

Wasps and bees and ants make up a group which occupies top place on the family tree of the insect world: partly because of their complicated anatomy but mostly because of the built-in-automatic features of their behavior which many people mistake for intelligence. Their elaborate ways of housing and feeding their young, or the division of labor among members of their colonies, do not signify intelligence. They merely inherit these instinctive traits.

The wasps include a multitude of kinds ranging in size from parasitic species almost invisible to the naked eye and reaching their full growth inside the tiny eggs of other insects, up to the giant Cicada-killers. Most kinds are so small or so scarce that they are seldom seen or recognized by ordinary people, but there are four types familiar to most of us in the middle west.

The Mud Daubers or "solitary wasps", the White-faced or "Bald-headed Hornets, the Yellow Jackets, and the Paper Wasps, rear their young in cells which are as precisely engineered as those in a honeybee comb but are made of mud or paper instead of wax. The last three are called "social wasps " because of their caste systems and the division of labor within their nests. Unlike bees, they feed their young on animal matter instead of nectar and pollen from flowers. We avoid wasps because a female defends her nest with a painful stinger and, unlike a honey bee, she can sting many times.

The common blue-black Mud Dauber typifies our expression "wasp- waisted" because its abdomen is a mere knob at the end of a long slender stem. As a female gathers mud and then trowels it into place at the chosen nest, she seems nervous, fidgety, and constantly jerks her iridescent wings. One by one, the tube-like mud cells are completed, stuffed with captured spiders, and egg placed in each, and then sealed. Each spider is paralyzed by a sting precisely placed so that it will remain inert but alive until the wasp's grub hatches out and needs it. When fully grown, the plump whitish grub weaves a silken cocoon inside the tube and changes into a pupa. Some emerge as adults that season; others in spring.

The other three familiar types, social wasps, are the world's finest papermakers. They chew up bits of weathered wood, waste paper and cardboard to build many-celled combs of tough membranes. The queen of the colony lays an egg in each cell. When it hatches, the grub is constantly tended and fed on chewed-up insects -- first by the queen; later by infertile female workers.

Hornets build an egg-shaped nest, often a foot in diameter, anchored on a branch of a tree or shrub, with many tiers of combs enclosed in sheets of gray flaky paper, and an entrance at the bottom. A Yellow Jacket's nest is similar but smaller and located in an old mouse nest underground, in a stump, or in a brushpile. Most commonly seen are the exposed unbrella-like combs of the Paper Wasp suspended, by short stems, under the eaves of houses or inside barns, sheds, and other sheltered places.

Among these social wasps, as with the bumblebee, only fertile queens survive the winter, and not in the old nest but hidden away in the walls of buildings, hollow trees, crevices under the bark of trees, or among trash. In spring she starts a new nest with a few cells which produce workers. Gradually, they take over and the queen is free for her main job of laying eggs. Later, certain grub are fed special diets so that some will develop into young queens. Males or drones come from unfertilized eggs.

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