Insect guide > Flies > Midges

Midges


(Family Chiroltomidae.)
The insects of this family, commonly known as "midges" are small, delicate flies with simple wing venation and no ocelli. The antennae of the males of most genera are strongly glucose, and the flies themselves are frequently seen flying in swarms with a dancing motion. When at rest the front legs of these flies are lifted and are used as feelers.

The larvae are mainly aquatic, but some live in decomposing matter and in soft earth. They are soft- skinned and worm-like in form and frequently blood- red in color. The aquatic forms are usually found in shallow pools and streams and make larval cases of silk and mud or decomposing leaves; but some are found at the bottom of lakes of great depth, Professor S. I. Smith having dredged them from the bottom of Lake Superior at a depth of nearly a thousand feet, and Packard has found them living in salt water in Salem harbor. The larva of Chironomus plumosus, figured herewith, abounds in great numbers in the waters of Chautauqua Lake and other fresh water lakes of the United States. These larvae form an important fish food but the family has no other economic value.

The flies abound in the spring, even before the snow has left the ground. Dr. Williston has seen them in the Rocky Mountains rise up from the ground at nightfall in the most incredible numbers, making a humming noise like a distant waterfall.

Many species are common to Europe and North America, belonging to the so-called "circumpolar fauna". The eggs of Chironomus are laid in the late evening or early morning in a dark gelatinous mass which swells up on touching the water and which is attached to some object close to the water's edge.

The larvae differ in form and habit, but there are two types. In one there are four long anal tubules which function as blood-gills, as in the fishes, and the pupae bear bunches of long filamentary tracheal gills. These larvae are large and red and are called in England "blood-worms". The larvae of the second type have no anal tubules and the pupa has a pair of short, breathing trumpets, as in the mosquitoes, in- stead of the thread-like tracheal gills. Larvae of the first type burrow; those of the second type often live at the surface of the water and feed on weeds.

These generalizations are taken from Miall and Hammond. One European species has been found to lay eggs while yet in the pupal stage. A genus of this family -Ceratopogon- is composed of very minute biting flies. The so-called "punkie" of the north woods, called "no-see-um" by the Maine Indians, belongs to this genus, and other species are found from Canada south to Chili.

Life History of a Midge
(Chironomus minutus)
The life history of no American species of this family has been worked out. That which follows is taken from the observations of Mr, L. H. Taylor, of Leeds, England, as given in the work on Ckironomus by the above mentioned authors. The larvae are found in gelatinous tubes attached to stones in slow or swift-running streams. When disturbed they leave their cases and crawl like measuring worms or swim with a figure-of-eight motion.

The larva is pale green in color and about seven mm. long and has no anal blood-gills. When about to pupate the thorax is much swollen. The pupae live in gelatinous cases attached to stones, each case having a slightly protruded orifice at either end so that the water flows through impelled by the unction of the body of the pupa.

The pupa breathes by means of respiratory trumpets which are so small as to suggest that the insect also breathes cutaneously or in some other way. It is armed with strong hooks on the abdominal segments by means of which, when mature, it tears its way through the case and rises to the surface of the water. In this position the skin of the thorax cracks and the adult fly emerges.