6 BULLETIN 329, U. S. DEPARTMENT OF AGRICULTURE. 
constant. If the claspers are large the basal portion is much smaller 
in proportion, and vice versa. 
There are three chitinous plates (a, a, a,) which are situated toward 
the dorsal surface of the hypopygium and surround the anal orifice. 
The two lateral plates are generally armed with spines or stout hairs. 
Ventrad of the plates and extending laterad on each side are two 
narrow chitinous flanges (am,, am) bearing mesally groups of strong 
spines, sometimes in a large number as in S. venustum and some- 
times reduced to only two as in S. hracteatum. These structures 
have been termed by Lundstrom the " arms." Ventrad of these 
spines and not easily distinguishable, extending inwardly, is a long, 
weak, chitinous piece, apparently the sheath of the penis. Ventrad 
and in front of this piece is a triangular troughlike sclerite called 
the adminiculum (ad), which is attached to two strong chitinous 
arms (st, st) , termed by Lundstrom the stylus. 
HABITS OF THE ADULTS. 
COPUEATION. 
The writer has found adults in copula flying near the stream from 
which they were emerging, but they at once separated on being dis- 
turbed. Dr. Sambon informed the writer that in Italy he has found 
the males resting on the reeds in swarms, apparently waiting for the 
females to emerge. 
Dispersion. 
It has been stated by several writers that the females travel long 
distances in search of food, but whether they are prompted by a 
desire for blood or are involuntarily carried away by the wind is a 
matter difficult to determine. 
The writer has been severely bitten by the females of S. johannseni 
Malloch and S. forbesi Malloch in the sand - dune region of 
Havana, 111., at a distance of 5 and even 6 miles from the only pos- 
sible breeding place, which was the Illinois River. The fact that 
the adults crossed a bare and sandy waste with little or no wind, and 
that no males were present, seems to indicate that their flight was 
voluntary. Eiley says that they may be carried 30 or 40 miles. They 
are sometimes attracted to light, as the writer has found a few speci- 
mens flying around a lamp at night. 
Feeding Habits. 
The adult female flies of all the species discussed in this paper, 
with the single exception of S. pictipes, 1 have been frequently ob- 
served feeding on the blood of mammals and, so far as the writer 
1 One female of this species, fully engorged with blood, was taken from a mule's ear by 
Mr. A. H. Jennings at Spartanburg, S. C, in 1912. 
