The Larva 



A typical " anopheles" egg (PL I, Figs. 2, 3) is a boat-shaped 

 body about 07 to I'O mm. in length. The upper surface or " deck " 

 is flattened, but slightly convex, and is surrounded by a narrow 

 beaded rim or frill. One end of the egg is slightly deeper and 

 fuller than the other, and it is toward this end that the head 

 of the embryo is directed. Along the centre of each side of the 

 egg is attached an oval ribbed air-containing " float" ( see also 

 Fig 8). These floats are very characteristic structures and are not 

 present in the eggs of any other kind of mosquito as yet described. 

 Their shape and position differ in the eggs of different species of 

 " anopheles," as does also the width and extent of the beaded rim or 

 frill already described, and Stephens and Christophers have shown 

 that it is possible to distinguish the eggs of some species by the 

 position and characters of these two structures. These distinctions 

 between the eggs of the various species will be described later. 



THE LARVA 



The larvae of all mosquitoes are made up of three regions : (1 ) 

 the head, (2) the thorax, and (3) the abdomen. The shape and 

 characteristics of these three regions differ in the various sub- fami- 

 lies, genera and even species of mosquitoes, but the characters of 

 the abdomen afford the readiest means of distinguishing between 

 the main groups and must therefore be described first. The abdo- 

 men of all mosquito larvae is divided into nine segments. The first 

 seven segments closely resemble one another and need not be spe- 

 cially described. The eighth segment carries the external openings 

 of the respiratory tubes or trachece, by means of which oxygen is 

 supplied to the tissues of the larva. In all " anopheles " larvae the 

 two large tracheae open directly on the upper surface of the eighth 

 segment by two stigmata which are surrounded and supported by a 

 complex apparatus (PI. I, Fig. 8). In "culex" larvae, on the other 

 hand, the respiratory tubes do not open directly at the surface of 

 the segment, but are prolonged onwards into a projection from the 

 segment known as the siphon tube (PI. I, Fig. 9). The absence of 

 a siphon tube in " anopheles " larvae renders their recognition from 

 among the larvae of all other kinds of mosquitoes an easy matter. 

 For the identification of the different kinds of " culex " larva? the 

 length and character of the siphon tube are of great value. Thus 



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