MOSQUITO 



309 



to dip out large numbers of larvae from the pools and having noted the character- 

 istics of the larvae, to do the same when the pupae develop; so that we have only to 

 verify our identification when the insect emerges from the pupa. 



THE OVA. 



The egg raft of Culex, containing about 250 ova, is quite perceptible on the 

 surface of the water as a black, scooped-out mass, about 1/5 of an inch in length. 

 The eggs are set vertically in the raft. The eggs of the Stegomyia are laid singly 

 and have a pearl-necklace-like fringe around them. 



ATE H/MRS 



~-- " UATERAL. ABDOM. HAIRS 



ANTENNA 



MOUTH BRUSH 



FIG. 91. i. Asiphonate larva. Anopheles. 2. Siphonate larva. Stegomyia. 



The Anophelinae eggs are oval in shape with air-cell projections from either side. 

 They are laid in triangle and ribbon patterns. The markings of these air cells 

 vary and have been used for differentiation. The length of time of the egg stage 

 varies according to temperature and other conditions one to three days for Stego- 

 myia and two to four days for Anophelinae. The Anophelinae are more difficult 

 to raise than Culex or Stegomyia. 



LARV.E. 



The 



There are two great classes of larvae the siphonate and the asiphonate. 

 latter are always Anophelinae. 



The Culicinae larvae have a projecting breathing tube at the posterior extremity 

 which is called a respiratory siphon. This projects off at an angle from the axis 



