Forest Preserve District of Cook County, Illinois
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Gnats and Midges
Nature Bulletin No. 529-A   May 11, 1974
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt of Conservation

Any small fly is commonly called a gnat or a midge, but flies of whatever kind are seldom popular, either large or small. True flies are insects with one pair of wings. Dragonflies, mayflies, stoneflies, fireflies, caddis flies and the like have two pairs of wings and are not flies. Some flies are useful as scavengers, and some help control destructive insects, but among the lot are most of the carriers of human diseases. The unpleasant habits of mosquitoes, house flies, deer flies, as well as certain gnats and midges, have given these diptera, or "two- wingers, " a bad name.

Black Flies, also called Buffalo Gnats, make life unbearable from May to midsummer for loggers, fishermen, campers and vacationers near streams in the resort regions of our northern states, Canada and the mountains. From dawn until dusk, except in bright sunlight, swarms of them fly about your head and get into your eyes, ears, nose and mouth. The females suck blood and inject a poison which raises big welts that itch and ooze for days, usually on the back of your hands and neck. If numerous, these bites can cause headache, fever and nausea .

The adults are stout, humpbacked, short-legged flies scarcely half as long as houseflies. The female dives into a stream and glues several hundred eggs to an underwater stone in rapid water. There the developing larvae use a fringe of finger-like tentacles around the mouth to strain food out of the water. Sometimes a rock is so crowded with these maggots that they look like patches of greenish black moss. After a few days as a pupa, it bobs to the surface, bursts, and a new adult takes wing.

Sand Flies, Punkies, or No-see-ums are other names for the Biting Midges. They breed in ponds, streams and tree holes. Their tiny slender larvae swim like miniature snakes. In many places they are a greater nuisance than mosquitoes, because their bite is like a jab with a red-hot needle and they are so small that they can enter dwellings through ordinary screens. Unfortunately they are most abundant after black flies and mosquitoes have had their season, and in places where the scenery is most beautiful.

Frequently, near lakes or streams, we see great swarms of little insects dancing over the water, or clustered against lighted windows at night. They look like small mosquitoes, the males with large feathery antennae. They sing like mosquitoes, too, but they do not bite. These are True Midges. Dozens or even hundreds of species of them breed in fresh water where both the adults and their larvae are a major source of food for almost all kinds of fish. Mature larvae of the different kinds range from a tenth of an inch to over an inch in length and, in color, may be white, yellowish, greenish, bluish, pinkish, or very deep red. The last, known as the "Blood Worm," is collected and sold in pet shops to feed aquarium fish. It thrives in moderately polluted water.

The young of other gnats and midges are plant pests. The Fungus Gnats cause "wormy" mushrooms. Others produce rose galls, chrysanthemum galls and the cone galls on willow. The most destructive of these gall midges is the Hessian Fly carried to America during the Revolutionary War in straw that the Hessian soldiers brought for bedding. Its annual damage to wheat, rye and barley is estimated at nearly a hundred million dollars.

You can't ignore the naughty gnat or the mighty midge.

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