ANOPHELES ROSSII : PUPA 203 



Herpetomonas and Crithidia, and the hind-guts of their larvae are 

 the chief situations in which the parasites undergo their early develop- 

 ment ; in an infected larva they may be seen in large numbers massed 

 together in the form of a palisade along the epithelial lining. 



Mosquito larvae moult three times, completely shedding their skins 

 before they are ready to pupate ; the organs of the imago commence 



to form during the last larval stage. The pupa emerges 



v f ^, . & , The pupa (Plate 



through a slit on the dorsal surface. Its appearance xxxiv fig. 6) 



is very characteristic ; it consists of a rounded body 

 composed of the head and thorax, and an elongated abdomen flattened 

 dorso-ventrally, and held underneath the body. The bulbous por- 

 tion is enclosed in a delicate cuticle, through which the appendages 

 of the developing imago can be readily made out. The antennae 

 appear as lateral ridges arising above and in front of the com- 

 pound eyes ; they pass backwards over the legs to end in front 

 of the wings. Arising from the dorsum of the thorax there 

 are two stout tubes, the respiratory trumpets. These are con- 

 stricted at their attached ends, but expanded distally, opening to 

 the exterior by a V-shaped slit, which is directed inwards and 

 guarded by a number of delicate hairs ; the narrow ends of the 

 trumpets are continuous with the lateral tracheae. Christophers has 

 pointed out that the shape of the slit and the manner in which the 

 trumpets project from the thorax are of generic significance. In 

 Anopheles the trumpets are short and arise from the middle of the dorsum 

 of the thorax, and have truncated ends ; in Culex they arise from the 

 posterior part of the thorax, are long and narrow, and the opening is 

 somewhat oblique, while in Stegomyia the tubes are short and broad, 

 and the openings triangular in shape. 



The abdomen of the pupa consists of nine segments, the first of which 

 is not clearly seen; its dorsal plate appears as a wedge between the 

 base of the wings. The second segment and the remaining six are 

 flattened dorso-ventrally; each dorsal plate is well developed, covering 

 almost the entire segment, and its sides are thickened and furnished 

 with posteriorly directed hairs. The eighth segment is armed with two 

 large chitinous flaps, the fins, each being supported by a stiff bar which 

 runs horizontally acjoss to end in a hair at the free margin. The 

 ninth segment has a pair of blunt processes lying between and in front 

 of the fins ; in the male they form a broad heart-shaped protuberance ; 

 in the female they are smaller, and thus afford a means of distinguishing 

 the sex- of the future imago. 



