SIPHONAPTERA AND DIPTERA 



31 



The adults are practically wingless, though small, scalelike projec- 

 tions from the top of the thorax show where the wings should be, and 

 perhaps once were. The body is flattened laterally, thus enabhng the 

 insect to slip around easily among the hairs of its host. While the sur- 

 face of the body is quite smooth and hard, it is provided with regular 

 rows of stiff bristles, pointing backward, which help to force the insect 

 in the direction in which it wishes to go, and likewise help it to escape 

 from the fingers of its captor. A further evidence of its parasitic life 

 is seen in the entire absence of compound eyes. The mouth parts are 

 fitted for sucking. 



Diptera 



The insects falling within this order are easily recognized from the 

 fact that they have only a single pair of membranous wings. The 

 order includes the groups that we speak 

 of as flies, mosquitoes, midges, and 

 gnats. 



Metamorphosis is complete. The 

 larva is commonly called a maggot, 

 and is without feet. In most species 

 it has no distinct head. In many sub- 

 groups within this order the pupa or 

 resting stage preceding the adult is 

 peculiar in that it is inclosed within 

 the hardened and shortened skin of 

 the larva. 



The single pair of wings borne by 

 the adult are on the middle segment 

 of the thorax. On the hind segment 

 are a pair of small knobs, represent- 

 ing the second pair of wings found in 

 other insects. 



The mouth parts are primarily of the sucking type, but often are 

 complex, and frequently are modified so that certain of the parts are 

 fitted for piercing or for rasping. Thus, in the horseflies there are 

 sharp lancets in addition to the sucking tube, the former penetrating 



Fig. 30. — Adult fly, Tabanus. 

 Enlarged to twice natural size. 

 Original. 



