THE EARLY STAGES OF CERTAIN WEST AFRICAN MOSQUITOS. 



143 



The thoracic plumes are formed of plumose hairs and are poorly developed. The 

 lateral abdominal hairs are multiple on the first segment, triple on the second 

 segment, and single on the remaining segments. The comb consists of 12-15 barbed 

 spines set in a triangular patch. All the hairs forming the siphonal, subsiphonal 

 and anal plumes appear to be subplumose. The siphon is slightly swollen about 

 its middle and is rather more than three times as long as the diameter of its base, 

 its pecten shows nine spines, which increase in length and are more widely separated 

 distally ; there is a slender tuft of simple hairs just beyond the middle (34/58). 

 The anal segment is longer than it is broad (23 : 19) ; the beard does not appear to 



Pig. 3. Larva of OcMerotatus minu'us, Tlipo. ; head and end of abdomen ; 



a, mental plat?. 



extend the full length of the ventral surface ; the hairs on the dorsal end of the 

 segment are a tuft of 5-6 hairs above and of one stout hair below on each side. The 

 anal papillae are short and bluntly pointed. 



This larva may be distinguished from other known African Ochlerotatus larvae 

 (Edwards' key, Bull. Ent. Res., iii, p. 376, and Bull. Ent. Res., vii, pp. 5-7) by the 

 fact that its multiple frontal hairs are delicately branched. 



Breeding place. — The larvae were found in April at the margin of a lagoon in 

 crab-holes that had been enlarged by children digging for crabs (Plate II, fig. 2). 

 The water in which they were living was dirty, thick with deposit, and quite salt. 

 In the same holes larvae and imagines of Culex thalassius were also found. 



The occupants of the house neighbouring the lagoon were much troubled by 

 mosquitos, and a small collection made on the same day as that on which the larvae 

 were found contained specimens of both 0. minutus and C. thalassius. 



