FLIES, MOSQUITOES, AND MIDGES 



233 



FIG. 369. Rat-tailed maggot, larva of 

 a syrphid fly similar to Fig. 368. (Twice 

 natural size) 



(After Kellogg) 



among colonies of plant-lice, around which the flies may be seen 

 hovering, and the maggots devour the aphides greedily, being 

 among their most important natural enemies. Some of the larger 

 species are thickly covered with yellow and black hairs, thus closely 

 resembling bumble-bees, in whose nests their larvae reside. A 



common species which is 

 often found on windows in 

 fall is known as the drone-fly, 

 from its close resemblance 

 to a honey-bee drone. Its lar- 

 va lives in foul water and 

 excrement, and is typical of 

 a group which is often found 

 in privies and similar filth. 

 The larva is maggotlike in 

 shape but has a long, extensile tube, through which it breathes, 

 projecting from the tip of the abdomen to the surface of the food- 

 material, which has given it the name of ' rat-tailed maggot." 

 None of the family seems to be injurious, and those larvae which 

 feed on plant-lice are exceed- 

 ingly beneficial. 



Bot-flies (Oestridae). Another 

 family in which the flies are well 

 covered with hairs, so as to 

 closely resemble bees, is that of 

 the bot-flies, whose maggots are 

 among the worst insect parasites FlG 3?0 A syrphus . fly ( volucella erecta] 



of domestic animals. The adults which resembles a bumble-bee and is an 



have very rudimentary mouth- inquiline in bumble-bees' nests (after 



S. T. Hunter); and a typical syrphus-fly 



parts, so that they probably take (Syyhns rtbesii} 



no food. The eggs are usually 

 laid on the hair of various animals, from which they are licked off 

 and pass into the alimentary tract, though others lay them upon 

 the lips or in the nostrils of the host. Among the more common 

 are the horse bot-fly, which gives rise to the bots in the stomach 

 of the horse, the ox-warble fly, whose maggots pass from the 

 stomach through the tissues of cattle and finally emerge through 

 holes in the skin, causing " grubby ' hides, and the sheep bot-fly, 



