374 ZOOLOGY 
and often to be found in sunny paths, etc. They lay their 
egos in bees’ hives, and the fleshy smooth maggots devour the 
larvae of the bees. 
Family SyrpHipAE—This is a family of brilliant yellow 
and black flies somewhat resembling wasps. They have a 
large head, and the eyes, which are very large, meet across 
the middle line in the male. They are found in sunny places, 
hovering motionless in the air, and then making a sudden dart 
at some flower upon whose nectar they feed. The genus 
Syrphus lays its eggs singly upon flowers, and the larvae feed 
upon Aphides, which are seized by the mouth parts situated 
at the end of the first segment ; this segment is then retracted 
into the second, and the second into the third. The larvae 
of other species are found in water or in bees’ nests; the 
rat-tailed larva of Hristalis is a well-known object in fresh 
water. Its body is prolonged posteriorly into a long respira- 
tory tube. 
Family Conoripar.—The members of this family also re- 
semble wasps, a resemblance which is probably partly protective, 
and which furthermore enables many of them to lay their eggs 
in or on the bodies of the insects they mimic. The Conopidae 
have a pedunculated abdomen, and their proboscis is unusually 
long, The eggs of Conops are probably laid on the soft tissue 
between the segments of some Hymenopterous insect, the larval 
and pupal stages are found within the body of the host, and 
the fly emerges between two of the abdominal segments, often 
breaking the abdomen of its host in two. 
Family OESTRIDAE (bot-flies)—The bot-flies have short, 
stout, hairy bodies, with minute antennae and rudimentary 
mouth parts. The eggs are laid on some place whence the 
parasitic larvae can easily effect a lodgment in its host. The 
larvae are thick, fleshy, apodal maggots, with eleven segments, 
which are usually provided with spines or hooks, by means of 
which they can move about within their host. Those which 
live in the alimentary canal of mammals have hooks, and attach 
themselves by these to the walls of the stomach. The stig- 
mata are borne on a horny plate at the posterior end of the 
animal, the end which is generally turned to the external 
world. The pupal stage is passed through on the ground. 
