162 
Arthropods as Simple Carriers of Disease 
parts of the country. Bishopp (1913) regards it as of much more 
importance as a pest of domestic animals in the grain belt than else¬ 
where in the United States. The life-history and habits of this 
species have assumed a new significance since it has been suggested 
that it may transmit the human diseases, infantile paralysis and 
pellagra. In this country, the most detailed study of the fly is that 
of Bishopp (1913) whose data regarding the life cycle are as follows: 
The eggs like those of the house-fly, are about one mm. 
in length. Under a magnifying glass they show a distinct furrow 
along one side. When placed on any moist substance they hatch 
in from one to three days after being deposited. 
The larvae or maggots (fig. 110) have the typical shape and actions 
of most maggots of the Museid group. They can be distinguished 
from those of the house-fly as the stigma-plates are smaller, much 
further apart, with the slits less sinuous. Development takes place 
fairly rapidly when the proper food conditions are available and 
the growth is completed within eleven to thirty or more days. 
The pupa (fig. no), like that of related flies, undergoes its develop¬ 
ment within the contracted and hardened last larval skin, or pu- 
parium. This is elongate oval, slightly thicker towards the head end, 
and one-sixth to one-fourth of an inch in length. The pupal stage 
requires six to twenty days, or in cool weather considerably longer. 
The life-cycle of the stable-fly is therefore considerably longer 
than that of Musca domestica. Bishopp found that complete 
development might be undergone in nineteen days, but that the 
average period was somewhat longer, ranging from twenty-one to 
twenty-five days, where conditions are very favorable. The longest 
period which he observed was forty-three days, though his finding 
of full grown larvae and pupae in straw during the latter part of 
March, in Northern Texas, showed that development may require 
about three months, as he considered that these stages almost cer¬ 
tainly developed from eggs deposited the previous December. 
The favorite breeding place, where available, seems to be straw or 
manure mixed with straw. It also breeds in great numbers in horse- 
manure, in company with Musca domestica. 
Ncwstead considers that in England the stable-fly hibernates in 
the pupal stage. Bishopp finds that in the southern part of the 
United States there is no true hibernation, as the adults have been 
found to emerge at various times during the winter. He believes 
that in the northern United States the winter is normally passed 
