46 INSECTS AFFECTING DOMESTIC ANIMALS. 
the presence of immense numbers of fresh-water sponges, polyps, and animaleula. 
Larvez of the Southern buffalo-gnat kept in glass vessels were observed to swallow 
these minute crustaceans, and none of this food was seen to be expelled again. 
A number of square diatoms, jointed together in a chain, have also been observed in 
Fig. 12.— Simulium 
pecuarum pupa—en- 
larged (from Riley). 
the intestines of these larvie by the aid of the microscope. 
The presence of such quantities of animal food will also account 
for the observed fact that the larvze grow so very rapidly dur- 
ing the early spring, since this is the time of the year in which 
most of the small fresh-water crustaceans spawn and produce 
living young, and food is, therefore, much more abundant at 
this season than at any other. 
When fully grown the larve descend to near the 
bottonr of the stream, sometimes 8 or 10 feet, to make 
their cocoons. 
The cocoon upon these leaves is conical, grayish or 
brownish, semitransparent, and has its upper half 
cut square off, more or less ragged, as if left unfin- 
ished. Its shape is irregular, the threads composing 
it very coarse, and the meshes rather open and ordi- 
narily filled with mud. They are not always fastened 
separately, but frequently crowded together, not forming, however, 
such coral-like aggregations as in some of the Northern species. The 
larva in spinning does not leave its 
foothold, but running in the center of 
its work uses its mouth to spin this 
snug little house. In it, it changes 
to a pupa, which has its anterior end 
protruding above the rim. 
The pupa (fig. 12) is, when fresh, of 
a honey-yellow color, the filaments of 
the front part of the body brown and 
the abdomen above tinged with brown. 
The filaments consist of Six main rays 
issuing from the basal prominence and 
subdivided two or three times, so that 
in most cases aS many as forty-eight 
terminal filaments can be counted. 
The color of the pupa changes with 
age, becoming pinkish, and, just be- 
fore emergence of the fly, black. 
‘During the first of these colora- 
tional epochs they are attached to the 
vegetable substance upon which the 
Fig. 13.—Simulium pecuarum: female, side 
view—enlarged (from Annual Report De- 
partment of Agriculture, 1886). 
pouch has been fastened by the thoracic filaments, by threads about 
the body, and by the anal extremity; but during the last two the 
pup hang by the short anal attachment alone to the threads at the 
bottom of the pouch and rise more and more out of it, until they swing 
freely in the current, attached only by the drawn-out threads,” 
eee Se eee 
