374 ZOOLOGY 



and often to be found in sunny paths, etc. They lay their 

 eggs in bees' hives, and the fleshy smooth maggots devour the 

 larvae of the bees. 



PamHy Syephidae. — 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-taUed larva of Uristalis is a well-known object in fresh 

 water. Its body is prolonged posteriorly into a long respira- 

 tory tube. 



Family Conopidae. — 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 Oesteidae (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. 



