The House-fly as a Carrier of Disease 
i45 
necessary that we define what is meant by “house-fly” and that we 
then consider the life-history of the insect. 
There are many flies which are occasionally to be found in houses, 
but according to various counts, from 95 per cent to 99 per cent of 
these in warm weather in the Eastern United States belong to the 
one species Musca domestica (fig. 108). This is the dominant house¬ 
fly the world over and is the one which merits the name. It has been 
well characterized by Schiner (1864), whose description has been 
freely translated by Hewitt, as follows: 
“ Frons of male occupying a fourth part of the breadth of the head. 
Frontal stripe of female narrow in front, so broad behind that it 
entirely fills up the width of the frons. The dorsal region of the 
thorax dusty grey in color with four equally broad longitudinal 
stripes. Scutellum gray with black sides. The light regions of 
the abdomen yellowish, transparent, the darkest parts at least at 
the base of the ventral side yellow. The last segment and a dorsal 
line blackish brown. Seen from behind and against the light, the 
whole abdomen shimmering yellow, and only on each side of the 
dorsal line on each segment a dull transverse band. The lower part 
of the face silky yellow, shot with blackish brown. Median stripe 
velvety black. Antennas brown. Palpi black. Legs blackish 
brown. Wings tinged with pale gray with yellowish base. The 
female has a broad velvety back, often reddishly shimmering frontal 
stripe, which is not broader at the anterior end than at the bases of 
the antennas, but become so very much broader above that the light 
dustiness of the sides is entirely obliterated. The abdomen gradu¬ 
ally becoming darker. The shimmering areas on the separate seg¬ 
ments generally brownish. All the other parts are the same as in 
the male.” 
The other species of flies found in houses in the Eastern United 
States which are frequently mistaken for the house or typhoid fly 
may readily be distinguished by the characters of the following key: 
a. Apical cell (R s ) of the wide wing open, i.e., the bounding veins 
parallel or divergent (fig. 100). Their larvae are flattened, the 
intermediate body segments each fringed with fleshy, more or 
less spinose, processes. Fannia 
b. Male with the sides of the second and third abdominal seg¬ 
ments translucent yellowish. The larva with three pairs 
of nearly equal spiniferous appendages on each segment, 
