Forest Preserve District of Cook County, Illinois
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Carpenter Ants
Nature Bulletin No. 598   April 2, 1960
Forest Preserve District of Cook County
Daniel Ryan, President
Roberts Mann, Conservation Editor
David H. Thompson Senior Naturalist

Cutting stove wood for home heating and cooking used to be a regular wintertime job. Then, when the trees are frozen solid, the work is easy. A large chunk of red oak, for example, pops wide open at a single stroke of the ax. Sometimes the fresh surface exposes a cluster of hibernating Carpenter Ants stiff and numb with cold inside a network of frost-lined tunnels. Warmed by the sun or the heat from a campfire they slowly begin to move their legs and feebly creep away.

In summer we see these carpenter ants prowling tree trunks and the forest floor in search of food. Occasionally, if we sit down on a fallen log or tap on a dead tree, dozens of them come rushing out with their antennae waving to see what is causing the disturbance. Less often, a colony is found enlarging its quarters. One ant after another runs out and drops a pellet of wood onto a pile of sawdust on the ground below, then hurries back inside for another load.

This long-legged fast-moving black ant is the largest in our region and among the largest in the world. It or its many near relatives, some with widely different habits, are found throughout the world in temperate and tropical climates. They are called social insects because they live in colonies in which there is a division of labor among the different members. The nests of our carpenter ant often look like ornate wood carvings with a maze of galleries polished as smooth as if they had been sandpapered. Termites, on the contrary, make channels which are cluttered with earthy material.

Usually, the colony is started in early summer by a young fertile queen which hides away in a crevice in a stump or injured place on a tree. There she lays a few eggs the size of pin points. These hatch into tiny larvae that grow into fat white grubs as they feed on her saliva, then change into pupae inside pale brown cocoons. From these cocoons small workers emerge which take over the grooming and feeding of their mother, the queen, the care of new broods of young and all of the housekeeping duties From now on the queen merely lays eggs.

As the colony grows, assorted sizes of workers appear; all are sterile females. The smallest are 1/4 inch long; the large "soldiers" are 1/2 inch in length. The queen is still larger, sometimes almost an inch, with a large head and bulging thorax kept highly polished by the constant licking and stroking by the workers. After the second or third year, young males and females with wings appear in the colony. In late spring these take flight and mate. The males soon die, the young queens shed their wings, then settle down to start new colonies.

Although carpenter ants bore holes in wood, either softened by decay or solid, unlike termites they do not eat wood. Like many other ants they coax honeydew from aphids, the so-called "ant cows". They also eat insects, live or dead.

Some of the interesting habits of these creatures can be studied by putting a dozen or two of these ants and some wood from their nest into a wide-mouthed jar closed with a piece of cloth and a rubber band. After they have quieted down for a few days, this can be connected by a glass or rubber tube with a smaller bottle or glass-topped box in which they are fed sugar water, dead insects, bits of cooked meat or boiled egg. Ants are blind to red so they can be watched undisturbed by a flashlight covered with red cellophane. A faint rustling in the walls of a house or rustic log cabin is sometimes due to the chewing of a colony of carpenter ants. Telephone poles, porch posts and the framework of buildings in contact with the soil are most often attacked. They are easily controlled with paint, creosote or insecticides.

Because they are so big, some people call them uncles.

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