ANOPHELES ROSSII : LARVA 197 



the V-shaped suture, there is another row of four smaller hairs, and 

 further back a pair of small simple hairs. 



The antennae arise from the sides of the head a little in front of its 

 middle point. They are generally described as two-jointed, the basal 

 joint being fused with the head wall. The projecting portion in rossii 

 is a simple cylindrical and tapering organ, usually directed forwards, 

 but capable of movement in a lateral direction. Its surface is sparsely 

 covered with short recumbent hairs, and at the distal end there are two 

 short spines, projecting from a papilla which is probably sensory in 

 function. In many species there is a plume of hairs on one side of the 

 antenna, inserted at varying distances from the base, and known as the 

 basal tuft. This is represented in rossii by a single short hair, easily 

 overlooked if the side on which it lies happens to be away from the 

 observer. The terminal portion at the base of the papilla may also bear 

 hairs, those found in this situation being usually shorter and stouter than 

 the proximal ones. The papilla itself may be lengthened though not in 

 Anopheles to form a distal joint. 



The eyes vary a good deal according to the age of the larva, as 

 both the primitive larval eye and the early stages of the developing eye 

 of the adult are present. The former is seen as a round or oval patch of 

 pigment situated behind the insertion of the antenna, while the com- 

 pound eye appears as a collection of isolated pigment spots slightly 

 dorsal to this ; they often show a crescentic outline. 



The ventral surface of the head is more irregular than the dorsal, 

 a considerable part of the anterior area being occupied by the mouth 

 parts. There is a median longitudinal suture extending forwards from 

 the collar, and a lateral suture some distance on each side of this. 



The mouth is adapted for the ingestion of minute particles, and is 

 provided with an apparatus for setting up a current in the water to 

 attract them, the larva remaining stationary or at the most turning round 

 in a circle as it feeds ; the particles are entangled in a sieve-like arrange- 

 ment of hairs, the water being discarded and the food swallowed. The 

 structures which form the mouth are the feeding brushes and certain 

 accessory bunches of hairs, the mandibles and first maxillae, and the 

 mental plate, with which is connected the hypopharynx. 



The feeding brushes are dense masses of long fine hairs, set one on 

 each side of the distal end of the head. Each is attached to a thickened 

 ridge of chitin at the side of the ventral margin, and is provided with 

 two muscles, by means of which it can be rotated inwards, and at the 

 same time retracted within the oral cavity. In the resting position the 



