196 MEDICAL ENTOMOLOGY 



Culicinae conform to a common type, of which, however, there are 



characteristic modifications in the different genera. Dyar and Knab have 



used the characters of the larvae as a basis for the 



External structure c i ass i ficat i on o f t h e Culicinae, and though there is at 

 of the larva . 



present no general agreement regarding the value of 



such larval characters, it is often a matter of practical importance 

 to be able to recognize species in their larval stage. Even the most 

 minute details of the external anatomy are, therefore, worthy of attention. 



As it is in the anopheline mosquitoes that differentiation is the most 

 important, Anopheles rossii will be taken as a type, the special char- 

 acters which are of use in separating species in this genus being empha- 

 sized. The modifications found in the Culicina will be referred to 

 subsequently. 



The head of the larva of A. rossii is roughly spherical, slightly flat- 

 tened in the dorso-ventral diameter, and narrowed in its anterior third, 



from the point of the insertion of the antennae. The 



The head and its , , ,. , ,, , . , , , . . , , 



appendages posterior border is slightly constricted, and is encircled 



by a collar-like rim of pigmented chitin, continuous 

 except at the middle line dorsally, where there is a slight interval. 

 From this point a V-shaped suture passes forwards, the two arms 

 diverging to extend to the inner side of the base of the antenna. In the 

 angle between the two limbs there are several symmetrically arranged 

 patches of dark brown pigment, forming a pattern which, although 

 subject to slight variation, is characteristic of the species. The dorsal 

 surface slopes rather sharply to the distal border of the head, where it 

 terminates in a slightly thickened transverse bar, termed by some writers 

 the clypeus, by others the labrum. Arising from, or slightly behind, 

 this border there are two pairs of hairs, termed the clypeal or frontal 

 hairs. The external pair of these project forward on each side over the 

 feeding brushes, and are on this account not always easy to distinguish. 

 The internal hair is set nearer the edge, and projects in the interval 

 between the feeding brushes. In rossii both these hairs are simple 

 and unbranched*, but in other species they may be forked or branched 

 forming a complete cockade, thus affording a valuable distinguishing 

 feature. About the middle of the head there is on the dorsal surface an 

 arched transverse row of six large feathered hairs, all of which project 

 upwards and forwards, reaching as far as the distal border of the head. 

 Behind these, and on each side of the pigment spots between the arms of 



*A hair is said to be branched when the branches lie in more than one plane, and 

 feathered when all are in one plane (Nuttall and Shipley). 



v 



