DIPTERA. et 
They remain in the pupa state but a short time. Both larval and 
pupal skins remain in the pouch for some time. 
The adult fly on emergence from the pupa rises quickly to the sur- 
face, runs a few inches over the water, and the wings expanding 
almost instantly it darts away. The fly (fig. 13 side view, 
fig. 14 dorsal view of female) is nearly a quarter of an 
| 2 inch in length, the female being somewhat larger than the 
male and differing in many respects. The color is black, 
but the body is covered with grayish brown, short, and 
silken hairs, which are arranged upon the thorax in such 
a manner as to show three parallel longitudinal black 
to stripes. The abdomen is more densely covered with simi- 
ie lar hairs and shows, furthermore, a broad dorsal whitish 
i stripe, which widens toward the posterior end. 
\f The male differs in the structure of the head (fig. 15; 
| head of male at the right; of female at the left), the eyes 
ef being larger, joining each other in the middle line, and = Fis. 14.—Simu- 
the individual facets being much larger on the upper part ets Saas 
of the eye, while those of the lower part (not correctly — from above— 
shown in the figure) are minute, the line of separation es ay 
between the two sizes being well marked. port Depart- 
The time of appearance of the swarms is regulated by = ment of Agri. 
the earliness or lateness of the spring, and consequently sgt ac 
it is much earlier in the southern parts of the Mississippi Valley. As 
a rule, they can be expected soon after the first continuous warm 
een 
| 
| = 
3 
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le 
| 
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he ; Fig. 15.—Simulium pecuarum: head of male, at right; head of female, at left—greatly enlarged (from 
Annual Report Department of Agriculture, 1886). 
weather in early spring. In 1885 the first swarms were observed in 
Louisiana March 11, in Mississippi and Tennessee May 1, and in 
Indiana and Illinois May 12. 
The accoants of its occurrence in December or other winter months 
do not seem to agree with the observations of recent years, but are 
i perhaps explicable on the ground of unusual seasons at the time of 
Such appearance, Small or local swarms may appear somewhat earlier 
