LIBRARY

DIPTERA 759
objects washed by spray and dashing currents or actually under the surface of
the water, and the larvre congregate in masses on the rocks in rapids, cascades,
and under waterfalls where they cling to the web spun from the mouth and
attached to the anchorage. The food, consisting of minute aquatic animals,
algre, and other plant life, is directed into the mouth by the brush-like hooks on
the head.
These insects are not only tormentors of wild and domestic animals and man
but cause painful swellings, and certain species like Eusimulium damnosum
(Theobald) of Africa transmit to man the filaria, Onchocera volvulus (Leuckart),
which causes a subcutaneous disease known as onchocerciasis. Their attacks on
domestic animals and poultry have caused wholesale deaths in parts of Europe
and North America. Folsom and Wardle (1934) call attention to the great
scourge of t.hese flies in Europe in 1923 when 16,474 domestic animals were
killed in Roumania by the attacks of swarms of the newly emerged adults of
what was probably Simulium columbaczense (Schiner), 2-3 mm., brown, which
has long been pestiferous along the Danube.
The family is relatively small as to species, there being only about 300, but,
as in many other families of flies, what is lacking in number of species is more
than made up in the great hordes of individuals which may overrun certain
areas within the scope of their habitats. Although many genera have been
described, only four important ones are now generally recognized. Of these
Prosimulium Roubaud and Simulium Latr. occur in Europe and Eusimulium
Roubaud, Parasimulium Malloch, Prosimulium Rob., and Simulium Latr.
inhabit North America. Simulium has by far the greatest number of species.
The most important North American species are: the Adirondack black fly,
Prosimulium hirtipes (Fries), which occurs in eastern North America; the
yellow gnat, P. fulvum (Coq.), a quick and hard biter in the western states;
Simulium bivittatum Malloch, a fierce biter, in the Pacific Northwest and ranging
from New Mexico to Montana; the turkey gnat, S. meridionale Riley, at
times a serious pest of turkeys, other domestic animals, and man, across the
southern part of the United States; the white-stockinged black fly, S. venustum
Say, with white marked tibire, in North America east of the Rocky Mountains
and north into Alaska; and S. vittatum Zetterstedt, the most widely distributed
species occurring throughout much of the continent.
Family CHIRONOMIDlE Rondani 1841 (Chi'ro-nom'i-dre, from the Greek
XELpOVOp.os, one who gestures with the hands; referring to the upraised,
waving forelegs). German, Schwarmmucken. Midges.
Minute to small, delicate, long-legged flies usually not more than 5 mm. and
rarely more than 10 mm. long. Head small, often partly hidden by thorax.
Antennre slender, hairy, basal segment globose, five- to 14-segrnented, plumose
in males. Eyes oval or reniform, smooth or pubescent. Ocelli absent or atrophied.
Mouth parts forming a short proboscis. not piercing, palpi three- to
four-segmented. Thorax large, with metanotal longitudinal groove. Legs
slender, long, fore pair often raised when resting; tibire with spurs; tarsi very