size after moulting twice. Just before
assuming the pupa state, the maggot 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 a
"puparium."

Several well-authenticated instances are on record of a species of bot
fly inhabiting the body of man, in Central and South America, producing
painful tumors under the skin of the arm, legs and abdomen. It is still
under dispute whether this human bot fly is a true or accidental
parasite, the more probable opinion being that its proper host is the
monkey or dog. In Cayenne, this revolting grub is called the Ver macaque
(Fig. 79); in Para, Ura; in Costa Rica, Torcel; and in New Granada,
Gusano peludo, or Nuche. The Dermatobia noxialis, supposed to be the Ver
moyocuil of the inhabitants of Mexico and New Granada, lives beneath the
skin of the dog.

[Illustration: 81. Bot Fly of Ox, and Larva.]

[Illustration: 82. Sheep Bot.]

[Illustration: 83. Skin Bot Fly.]

The Bot fly of the horse, (Gastrophilus equi, Fig. 80 and larva), is
pale yellowish, spotted with red, with short, grayish, yellow hairs, and
the wings are banded with reddish. She lays her eggs upon the knees of
the horse. They are conveyed into the stomach, where the larva lives
from May until October, and when full grown are found hanging by their
mouth hooks on the edge of the rectum of the horse, whence they are
carried out in the excrement. The pupa state lasts for thirty or forty
days, and the perfect fly appears the next season, from June until
October.

The Bot fly of the ox (Hypoderma bovis, Fig. 81, and larva), is black
and densely hairy, and the thorax is banded with yellow and white. The
larva is found during the month of May, and also in summer, living in
tumors on the backs of cattle. When fully grown, which is generally in
July, they make their way out and fall to the ground, and live in the
pupa-case from twenty-six to thirty days, the fly appearing from May
until September. It is found all over the world. The Oestrus ovis, or
sheep Bot fly (Fig. 82, larva), is of a dirty ash color. The abdomen is
marbled with yellowish and white flecks, and is hairy at the end. This
species of Bot fly is larviparous, i.e., the eggs are hatched within the
body of the mother, the larvae being produced alive. M. F. Brauer, of
Vienna, the author of the most thorough work we have on these flies,
tell