MOSQUITOES AND FLIES 



mosquito to lay her eggs upon the surface of the water, 

 and that the larvae come from the eggs. 



There are many species of mosquitoes, but, from the 

 standpoint of human interest, most of them are included 

 in three groups. First there are the "ordinary" mos- 

 quitoes, species of the genus Culex or of related genera; 

 second, the yellow- fever mosquito, Aedes aegvpti; and 

 third, the malaria-carrying mosquitoes, which belong to 

 the genus Anopheles. 



The common Culex mosquitoes (Fig. 174 A) lay their 

 eggs in small, flat masses (C) that float on the surface of 

 the water. Each egg stands on end and is stuck close to 

 its neighbors in such a manner that the entire egg mass 

 has the form of a miniature raft. Sometimes the eggs 

 toward the margin of the raft stand a little higher, giving 

 the mass a hollowed surface that perhaps decreases the 

 chance of accidental submergence, though the raft is 

 buoyed up from below by a film of air beneath the eggs. 



Almost any body of quiet water is acceptable to the 

 Culex mosquito as a receptacle for her eggs, whether it be 

 a natural pond, a pool of rainwater, or water standing in 

 a barrel, a bucket, or a neglected tin can. Each egg raft 

 contains two or three hundred eggs and sometimes more, 

 but the largest raft seldom exceeds a fourth of an inch in 

 longest diameter. The eggs hatch in a very short time, 

 usually in less than twenty-four hours, though the in- 

 cubation period may be prolonged in cool weather. The 

 young mosquito larvae come out of the lower ends of the 

 eggs, and at once begin an active life in the water. 



The body of the young mosquito larva is slender and 

 the head proportionately large (Fig. 174 D). As the 

 creature becomes older, however, the thoracic region of 

 the body swells out until it becomes as large as the head, or 

 finally a little larger (E). The head bears a pair of lateral 

 eyes (Fig. 175, b), a pair of short antennae {Ant), and, on 

 the ventral surface in front of the mouth, a pair of large 

 brushes of hairs curved inward {a). From the sides of 



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