ANOPHELES ROSSII : LARVA 199 



plate consists of two parts, one lying dorsal to the other, so that they 

 appear as one when seen from above. The upper of these would corre- 

 spond to the mentum, which has become displaced backwards behind the 

 submentum. The salivary duct traverses the median area and opens at 

 its tip. 



The larva of Anopheles is a surface feeder, and therefore assumes an 

 attitude parallel with the surface, retaining its position by means of the 

 palmate hairs on the abdomen. The head can be rotated through 

 an angle of 180, so that the ventral surface becomes dorsal. The feeding 

 brushes are moved rapidly inwards, and at the same time retracted, a 

 succession of these movements setting up a current which carries any 

 solid particles within reach towards the mouth. They are then secured 

 and swallowed, while the water is allowed to escape. From time to time 

 the stout hairs on the mandibles, and the shorter hairs on the maxillae, 

 are used to remove the particles from the brushes, and to rearrange them. 



The thorax, like that of the adult, does not show any clear divi- 

 sions into segments. It is rounded in shape, and bears on its dorsal 



and lateral surfaces three rows of feathered hairs. The 



r . . , ' , Thorax and abdomen 



most anterior of these is situated at the front margin, 



and consists of six hairs which overhang the head. The second row 

 lies a little behind the first, while the third, which consists of larger 

 hairs than the preceding, is placed at the junction of the middle with 

 the anterior third. The thorax is relatively much larger in adult than 

 in young larvae, and in some species of Anopheles it may be furnished with 

 palmate hairs, like those on the abdomen, to be described presently. 



The abdomen consists of nine segments, diminishing gradually in 

 size from before backwards. The first seven resemble one another, 

 and are broadest in the transverse diameter ; the eighth bears the 

 respiratory opening, and the ninth the anus, with certain special struct- 

 ures. Each of the first three segments is furnished with a pair of long 

 feathered hairs, directed forwards and outwards, and inserted on slightly 

 raised areas at the lateral borders. The remaining segments are armed 

 with simple hairs, and there are on each segment several smaller ones, as 

 well as on the raised: lateral areas. None of the structures afford 

 reliable distinguishing characters. 



The palmate hairs (Plate XXXV, fig. 17) are minute but elaborate 

 structures, by means of which the larva is enabled to cling to the 



surface film. They are situated on the lateral part 



,, , , , - , ., ., Palmate hairs 



of the dorsal surface of the abdominal segments, and 



are peculiar to the Anophelina. The number varies in different species ; 



