356 COLLEGE ZOOLOGY 



pellionella (Fig. 290), injures animal textiles of all kinds. Its 

 larvae feed on fur, feathers, woolen fabrics, etc. The larvae 

 of the grain moth, Gelechia cerealella, bore into kernels of 

 wheat, rye, and corn. 



Order 16. Diptera. — Flies (Figs. 291-295). — Insects with 

 two wings attached to the mesothorax; the metathorax bears 

 knobbed threads, the hal teres; sucking mouth-parts; meta- 

 morphosis complete. 



This is one of the largest orders of insects, there being about 

 seven thousand known species in North America. These may- 

 be grouped as follows: 



Suborder i. Diptera genuina (true flies). 

 Section 1. Nematocera (long-horned flies). 

 Section 2. Brachycera (short-horned flies), 



Suborder 2. Pupipara (ticks and lice). 



The Nematocera include the mosquitoes, crane flies, gall- 

 gnats, midges, and black flies. 



The mosquitoes (Culicid,e) have an interesting life-history. 

 The eggs are laid on the surface of the water in a raft-like mass 

 (Fig. 291, b) or singly. The larvae live in the water and are 

 known as wrigglers (Fig. 291, c); they have an air tube on the 

 abdomen which is thrust through the surface film of water. 

 The pupa is likewise aquatic. The adult male differs from the 

 female (Fig. 291, a) in the structure of the antennae and in feed- 

 ing habits. Only the females suck blood; the males, if they 

 eat at all, pr»obably feed on nectar. It has been proved by 

 experiments that mosquitoes of the genus Anopheles transmit 

 human malaria (see Chap. II), and that individuals of the 

 genus Stegomyia transmit yellow fever germs. The larvae and 

 pupae of mosquitoes may be destroyed by draining pools and 

 swamps or by covering the water with a thin layer of oil, which 

 prevents them from obtaining air. 



The crane flies (Tipulid^e) look like large mosquitoes. The 

 gall-gnats (Cecidomyiid^e) are terrestrial during their entire 

 lives. Their common name has been given to them because 



