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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
GNATS AND MIDGES
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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Update: June 2012
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