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. 



Vepitrad 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 8. venustum and some- 

 times reduced to only two as in 8. bracteatum. These structures 

 have been termed by Liindstrom 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 Liindstrom the stylus. 



HABITS OF THE ADULTS. 



Copulation. 



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 8. johannseni 

 Malloch and 8. 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. Riley 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 8. piqtipes, 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. 



