i} No. 71, REVISED EDITION. 
nited States Department of Agriculture, 
BUREAU OF ENTOMOLOGY, 
L. O. HOWARD, Entomologist and Chief of Bureau. 
HOUSE FLIES. 
(Musca domestica et al.) 
By L. O. Howarp. 
There are several species of flies which are commonly found in houses, 
although but one of these should be called the house fly proper. This 
is the Musca domestica L. (fig. 1) and is a mediuni-sized, grayish fly, 
with its mouth parts spread out at the tip for sucking up liquid sub- 
stances. It breeds in manure and dooryard filth and is found in nearly 
all parts of the world. On account of the conformation of its mouth 
Fig. 1.—Common house fly (Musca domestica): Puparium at left; adult next; larva 
and enlarged parts at right. All enlarged (author’s illustration). 
parts, the house fly can not bite, yet no impression is stronger in the 
minds of most people than that this insect does occasionally bite. This 
impression is due to the frequent occurrence in houses of another fly 
(Stomoxys calcitrans L.) (fig. 2), which is called the stable fly, and 
which, while closely resembling the house fly (so closely, in fact, as 
to deceive anyone but an entomologist), differs from it in the important 
particular that its mouth parts are formed for piercing the skin. It is 
perhaps second in point of abundance to the house fly in most portions 
of the Northeastern States. 
A third species, commonly called the cluster fly (Pollenia rudis Fab.), 
is a very frequent visitant of houses, particularly in the spring and fall. 
This fly is somewhat larger than the house fly, with a dark-colored, 
smooth abdomen and a sprinkling of yellowish hairs. It is not so active 
as the house fly and, particularly in the fall, is very sluggish. At such 
