68 DIPTERA. 



many noxious insects ; and very many species, while in the larval state, 

 feed upon decaying animal and vegetable matter, thus acting as scavengers. 



Although the habits of these creatures, which revel in all kinds of filth 

 are very disgusting, we cannot help admiring that arrangement by which 

 a mass of filth, instead of being left to poison the atmosphere, is transform- 

 ed into myriads of living beings, whose swift flight and delicate forms 

 lend life and beauty to the landscape. 



Only a few species, illustrating the more important families, can be dis- 

 cussed in this course. 



CULICID/E {Mosquitoes or Gnats). 



Most N. Am. .species of this family belong to the 

 genera Culex and Anopheles. These genera may be 

 separated as follows : " The palpi of Culex (males) are 

 longer than the proboscis, whilst in Anopheles the 

 palpi are of the same length." (21, pi.. A). 



Culex. — More than thirty N. Am. species have been 

 described. Eggs laid in boat-shaped masses. Larvre 

 called " wigglers," aquatic, breathing through a respi- 

 ratory tube, placed on the eighth abdominal segment. 

 Pupa; active, respiratory tubes thoracic, two in number. 

 "The female insects sting severely and suck blood, 

 whilst the males content themselves with the juices 

 or nectar of flowers." (21, 16). The larva; are benefi- 

 cial, acting as scavengers. There are several broods 

 each year. 



Cecidom Yl D.K {Gall-gnats).* 



These insects lay their eggs in stems, leaves, buds, 

 and flowers of various plants. The larva; produce 



■ See monograph of this family by Baron Osten S.i(;ken in the Smithsonian Mono- 

 graphs of North Amcricpp Tiptcra, Part i. p 173. 



