6 
and continuous breeding ina tropical region like the Hawaiian Islands. 
The winter habits as studied near Washington, D. C., indicate that 
hibernation normally takes place either in the adult stage or as 
puparia below the surface of the ground. 
PARASITES AND NATURAL ENEMIES. 
The natural enemies of the horn fly, like those of most other dung- 
breeding flies, are destructive to the insect in its larval and pupal 
stages. Therefore the bringing over of the insect from Europe in the 
adult stage with cattle resulted necessarily in its freedom for a time 
from the control by such natural enemies. The similar enemies of 
other dung flies in this country, however, undoubtedly very soon 
began to exercise a certain degree of control, and this may account 
Fic. 3.—Horn fly: a, Head of female, front view; b, head of male, front view; c, head from side. Greatly 
enlarged. (From Riley and Howard.) 
somewhat, at least, for the much greater damage occasioned by the 
horn fly in the first years of its occurrence in the different zones of 
its spread across the continent than was the case during subsequent 
years. Very early after the appearance of the horn fly it was noted 
by Mr. F. M. Webster that in Ohio fully, 20 per cent of the flies were 
infested by one of the scarlet mite fly parasites (Gamaside). This 
mite was not determined, but was probably one of the native species 
commonly seen on other flies. 
The introduction of the horn fly into the Hawaiian Islands and the 
heavy losses there occasioned by it led to an active investigation on 
the part of the island authorities of parasites and predaceous enemies. 
Mr. Albert Koebele imported, in 1905, from New South Wales, quan- 
tities of material from which dung beetles were reared and introduced 
into the islands. In 1906 Mr. Koebele came to the United States and 
made extensive collections of material in California and Arizona, and 
from this material at least six or seven species of dung beetles were 
introduced into the Hawaiian Islands, and two species of true parasites. 
[Cir. 115] 
