266 



ORDER DIPTERA 



of the pools to destroy the adult females, and this seems to 

 have been very successful. The trouble in this is that the 

 kereosene kills other forms of life which are not obnoxious. 

 There are several species in this locality. The species com- 

 mon about horses are the green heads and the big black flies. 

 The green heads sometimes cause a great deal of trouble. 



The remaining families of the order come in the suborder 

 Cyclorhapha. This group includes an immense number of 

 flies, many different families and some of the families an 

 immense number of species. 



Fig. 212.— Tabanus atratus. 



larva; b, pupa; c, adult. (After Riley.) 



The first important family in the group is that known as 

 the SyrphidoB. This one family presents about as great a 

 variety of life, habit and conditions as any in the order. 

 There is everything from aquatic to arboreal species in the 

 larvse. The rat-tailed forms which live in liquid have a long 

 tube extending to the surface of the liquid. Another species 

 occurs on trees. The more important economically are 

 the ones that feed on plant lice, and these are a most impor- 

 tant factor of control. Many species mimic members of 

 other groups of insects. Some look very much like wasps, 



