32 



HOW INSECTS ABE CLASSIFIED 



the tissues and assisting in bringing on a generous flow of blood, which 

 the latter conveys to the insect's pharynx. In the female mosquito 

 similar structures are found, sharp stylets penetrating the flesh and the 

 pharynx pumping the blood up through a sucking tube. 



The antennae are of various shapes, from the elaborately feathered 

 structures of the male mosquito to the short, peculiar form, orna- 

 mented with a prominent bristle, found in manj^ of the so-called 

 ''flies." 

 Classification within the order is complex, and is based partly on the 



manner in which the pupal 

 skin is ruptured when the 

 adult emerges, partly on 

 the tj^pe of antenna, partly 

 on the arrangement of the 

 veins in the wings, as well 

 as other structural pecul- 

 iarities. 



More than 40,000 species 

 have been described. 



The number of families 

 is very large, but among 

 the more important groups 

 may be mentioned the 

 following : 



Culicidae, the mosqui- 

 toes. A nuisance to man 

 and domestic animals, and in some cases carriers of disease. Larvae 

 aquatic, as a rule. 



Chironomidse, the midges (but not the so-called midges attacking 

 wheat, clover, and the like). Larvae often aquatic. 



Cecidomyiidae, the gall midges. Many injurious species, some of 

 prime importance, as the Hessian fly. 



Simulidae, the black flies. Attack man and domestic animals. 



Tabanidae, the horseflies. 



Asihdae, the robber flies. Predaceous on other insects. 



Fig. 31. — Adult mosquito. Enlarged and 

 natural size. Original. 



