THE DIPTERA OR FLIES 



45 



ful and graceful midges; and the gall gnats, Cecidomyiidse, 

 which include the destructive Hessian fly which causes 

 so great a damage to wheat fields. 



It is desirable, however, to treat of the mosquitoes a 

 little more fully, since these insects are perhaps the most 

 important of all the insect enemies of man. Mosquitoes, 

 like house flies, produce several broods a year. The fe- 

 males deposit their cigar-shaped eggs upon the surface of 

 quiet water, some species placing them side by side with 

 their pointed ends upward form- 

 ing a sort of "raft" that floats 

 on the water. The egg at ordi- 

 nary summer temperature 

 hatches in less than a day into 

 a small, large-headed wriggler 

 which is commonly seen attached 

 at the surface of the water by 

 its breathing tube situated near 

 the posterior end of the body. 

 The wrigglers live upon minute 

 organisms and organic matter in 

 the water, and they may often be PIG 35 ,_ Culex pungens . 



found feeding near the bottom. Female above, male below. 

 m Feet, /, and scales, s, enlarged. 



Iney are under the necessity of (After Howard.) 

 coming to the surface for air 



at rather frequent intervals. After a number of molts 

 the larva passes into a pupa stage which is peculiar in 

 being active and in suspending itself, like the larva, at the 

 surface of the water. Instead of having a posterior 

 breathing tube, however, the pupa has a pair of such 

 tubes attached to the greatly enlarged thorax. Project- 

 ing below the thorax may be seen the wing cases and leg 

 cases which are closely fused to the body. The pupa 



