594 A CHAPTER ON FLIES. 
long as it is thick. The case itself is cylindrical, and 
rounded alike at each end. 
We now come to the Bot-flies (Wstridw), which are 
among the most extraordinary, in their habits, of all insects. 
The history of the bot-flies is in brief thus: The adult two- 
winged fly lays its eggs on the exterior of the animal to be 
infested. They are conveyed into the interior of the host, 
where they hatch, and the worm or maggot lives by sucking 
in the purulent matter, caused by the irritation set up by its 
presence, in its host; or else the worm itself, after hatching, 
bores under the skin. When fully grown, it quits the body 
and finishes its transformations to the fly-state under ground. 
Many quadrupeds, from mice, squirrels and rabbits, up to 
the ox, horse, and even the rhinoceros, suffer from their 
attacks, while man himself is not exempt. The body of the 
adult fly is stout and hairy, and it is easily recognized by 
having the opening of the mouth very small; the mouth- 
parts being very rudimentary. The larve are, in general, 
thick, fleshy, footless grubs, consisting of eleven segments, 
exclusive of the head, which are covered with rows of 
spines and tubercles, by which they move about. within 
the body, thus irritating the animals in which they take up 
their abode. The breathing pores (stigmata) open in 4 
scaly plate at the posterior end of the body. The mouth- 
parts (mandibles, etc.) of the subcutaneous larvæ consist 
of fleshy tubercles, while in those species which live in the 
stomachs and frontal sinuses of their host, they are armed 
with horny hooks. The larve attain their full size after 
moulting twice. Just before assuming the pupa state, the 
larva leaves its peculiar dwelling-place, descends into the 
ground and there becomes a pupa, though retaining its larval 
skin, which serves as a protection to it, whence it is called & 
“puparium.” = > | 
Several well-authenticated instances are on record of p 
species of bot-fly inhabiting the body of man, in Central - 
and South America, producing painful tumors under the 

