LIBRARY

DIPTERA 799
riorIy; distinctly segmented; ventral pseudopods present; four or more tubercles
above the spiracular area; metapneustic; the pair of posterior spiracles
hemispherical and each with three radially arranged, slit-like openings; anterior
spiracles each with six to eight processes; 6-10 mm. long. Pupee enclosed
FIG. 299. The common housefly, Musca domestica Linn., a species long associated
with the human race. (After Gibson and Twinn, 1931.)
in last larval skin (puparium); yellowish or reddish-brown, oval; 3-6 mm. long;
segmentation visible.
As now constituted, this is a small family of some 25 genera and about 100
species that make up a group of closely related saprophagous species. As larvre,
they are of little or no consequence, but the a,dults, which often appear in great
multitudes, are a source of much annoyance to man. A number of species trana·