GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 30 
according to species, and placed under favorable rearing conditions. 
Tt is evident that larve within the stomach and duodenum are not 
capable of withstanding the internal processes which accompany 
the decomposition of animal tissues, especially during warm periods. 
There is excessive gas formation with the breaking down of the tis- 
sues, and the larve apparently become asphyxiated, since they are 
found bloated and when crushed become flat. During cool periods 
larvee are affected very little for a number of hours, and in stated 
cases as long as 30 and 48 hours after death of the host larve have 
been reared to adults. Low temperatures hold back that period of 
decay in the carcass which normally would cause the death of larvee. 
From post-mortem examinations, as will be seen in Table I, 
G. haemorrhoidalis larvee are seldom found in the rectum. In all 
probability they drop shortly after death, and during the normal 
period of dropping are capable of producing adults. 
CONTROL STUDIES. 
REMOVAL OF G. HAEMORRHOIDALIS LARVA FROM RECTUM. 
The effectiveness of the extraction of Hypoderma larvee as advocated 
by various authors suggests a mechanical removal of G. haemorr- 
hoidalis larve. While they appear at the margin of the anus daily, 
studies show that they remain visibly attached from 40 to 71 hours. 
This would necessitate much work during a busy season with farm- 
ers, but extractions at feeding time would greatly reduce the number 
in work animals. In practice this periodical detaching caused much 
discomfort and soreness about the anus. 
The attachment of clusters of larve within the rectum and the 
recommendation of tobacco decoctions, by the Bureau of Animal 
Industry (1911), for larve lodged in the rectums of horses, indi- 
cated the need of information as to the effect, on this species of 
Gastrophilus, of substances used as enemas. This necessarily re- 
quired a detailed study of the effects of various substances upon 
larvee, and these are reported in Table VIII. 
