132 



SCHOOL ENTOMOLOGY 



that were previously considered as merely annoying pests 

 has opened up a new field in the study of insects 



known as Medical En- 

 tomology. 



81. Fly Larvae. Fly 

 larvae are footless and 

 sightless but fairly act- 

 ive in spite of these 

 handicaps. They feed 

 to some extent on grow- 

 ing plants, either on or 

 in the roots, foliage, or 

 fruit, but by far the 

 larger number of them 

 are scavengers, feeding 

 on decaying animal and 

 vegetable matter of 

 every description. Some 

 fly larvae grow with ex- 

 traordinary rapidity. 

 This is especially true of 

 the forms that feed on 

 dead animals, probably 



because the decaying flesh remains in a condition fit for 

 food for a limited time only. 



82. Classification. The classification of the Diptera is 

 difficult for the beginner. This is largely because a use 

 of most of the descriptions and tables for the order, in- 

 volves wing-venation characters which are usually rather 

 complicated and will not be considered here. It is some- 

 what difficult to characterize even the more common 

 families so that the beginner can easily distinguish 

 them. For this reason no attempt will be made to de- 



FIG. 97. House-fly (above) and Stable 

 Fly, Showing Lapping Mouth-parts 

 and Piercing Beak. Enlarged. 



