84 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. 
time they would attach to a piece of paper or stomach section or even 
to one another. This is only a temporary attachment, however, and 
apparently no attempt at feeding takes place. 
The studies of Brauer, Numan, and Guyot indicate that the larvee 
molt during their development and that there are at least three 
stages. No experiments have been reported as to the exact time that 
Jarve remain within the body of the horse, although apparently they 
spend about 10 months in this parasitic stage. On some occasions, 
as will be observed in Table I, well-developed larvee were disclosed on 
post-mortem examinations in early fall. The indications are that 
some larve are not sufficiently developed to pass out in time to pro- 
duce adults and that they succumb to low temperatures. There are 
various factors that apparently tend to influence the extension of lar- 
val periods. When gross infestations occur the development is 
markedly slower than in those horses containing only a few larvee. 
Laxative foods have a greater tendency to discharge well-developed 
larvee than foods of a non-laxative nature, as is observed in comparing 
autopsies of livery and pastured animals. Since there is such a wide 
range of variation in the ages of larve within the eggs at which they 
are capable of being ingested it is possible that this may tend to 
prolong the period during which the last-stage larvee drop. - 
SUBMERGENCE OF LARVA. 
Last-stage larvee removed from horses immediately after death 
remained alive and active from 21 to 33 days when submerged in 
water, but when submerged for only 6 days they would not attempt 
pupation. These periods are considerably decreased if larvee are 
not removed shortly after the death of the animal. 
PUPA PERIODS. 
The larve drop naturally with manure, burrow only enough for 
protection, and normally pupate within a day or two. The periods 
of dropping extend over a long time and very few larve are 
found in droppings. It is a difficult matter to rear larve taken 
in post-mortem examinations, and this is best undertaken in the late 
summer or early autumn, when the greatest number of larve are 
fully developed. With such larvee, used in the experiments, the pu- 
pa periods have been observed to vary from 27 to 43 days, with an 
average of 38 days. 
EFFECT OF DEATH OF HOST UPON GASTROPHILUS LARVA. 
The resistance of larvee and the death of horses from infectious 
diseases naturally suggest the fate of larva during the period when 
they normally drop. In experiments larve were not kept with the 
animals during the decay, but were removed in autopsies, separated 
