6 HOUSE FLIES. 
sluggish. At such times it may be picked up readily and is very 
subject to the attacks of a fungous disease which causes it to die upon 
window panes, surrounded by a whitish efflorescence. Occasionally 
this fly occurs in houses in such numbers as to cause great annoyance, 
but such occurrences are comparatively rare. It is said in its earlier 
stages to be parasitie on certain angleworms. 
A fourth species is another stable fly, known as Muscina stabulans 
Fall. (fig. 3), a form which almost exactly resembles the house fly in 
general appearance, and which does not bite as does the biting stable 
fly. It breeds in decaying vegetable matter and in excrement. 
Several species of metallic greenish or bluish flies are also occasion- 
ally found in houses, the most abundant of which is the so-called blue- 
bottle fly (Calliphora erythrocephala Meig.). This insect is also called 
the blow-fly or meat-fly and breeds in decaying animal material. A 
Fig. 2.—The stable fly or biting house fly (Stomorys calcitrans): Adult, larva, puparium, and 
details. Allenlarged. (Author’s illustration.) 
smaller species, which may be called the small blue-bottle fly, is 
Phormia terrenove Desv. (fig. 4); and a third, which is green or 
blue in color and a trifle smaller than the large blue-bottle, is Luctha 
cesar L. (fig. 5). 
There is still another species, smaller than any of those so far men- 
tioned, which is known to entomologists as Homalomyia canicularis 
L., sometimes called the small house fly. A related species, H. brevis 
Rond., is shown in figure 6. H. canicularis is distinguished from the 
ordinary house fly by its paler and more poimted body and conical 
shape. The male, which is much commoner than the female, has 
large pale patches at the base of the abdomen, which are translucent 
when the fly is seen on a window pane. It is this species that is 
largely responsible for the prevalent idea that flies grow after gain- 
ing wings. Most people think that these little Homalomyias are the 
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