Species of Anopheles 49 



Knab. The chief differentiating larval characters of 

 the common anopheUnes of this region are these: 



A. albimanus or white-footed group: 



Palmate hairs on all abdominal segments and some- 

 times on postero-external angle of the thorax. 



AntennEe without a tuft of hairs. 

 A. pseudopunctipennis group: 



Palmate hairs on third, fourth, fifth, sixth, and 

 seventh abdominal segments, but none on the 

 first and second. On the latter two, however, 

 there is a rudimentary stalked tuft replacing 

 the palmate hairs. 



Antennae without a tuft of hairs. 

 A. malefactor or spotted-legged group: 



No palmate hairs on first and second abdominal 

 segments, but palmate hairs on all remaining 

 segments. 



Antennae with a tuft of hairs. 



These characters are very striking and sharply sep- 

 arate the malaria transmitting A. albimanus group 

 from other varieties. With care it is frequently 

 possible even in muddy water, from an examination of 

 the indentations of the surface film caused by the 

 palmate hairs, to at once determine the presence or 

 absence of members of the A. albimanus group. In 

 this group there is no break in the indented fikn, but 

 in the two other groups there is a well-defined non- 

 indented break in the film, due to the lack of palmate 

 hairs on the first and second abdominal segments. 



The size of the palmate hairs on the postero-lateral 

 angle of the thorax, and the presence of these hairs on 

 the thorax, first and second abdominal segments, is 



