554 



THE ANIMAL PARASITES OF MAN 



Sexual Organs of the Mosquito. The female has a pair of ovaries, opening into 

 a single tube by the ovarian tubes ; into the single tube opens a duct coming from 

 the spermathecse, and also a mucous gland. The spermathecae store up the male 

 cells. The male organs consist of two testes joined by ducts (vasa deferentia) to the 

 ejaculatory duct formed by their union. Each vas deferens is joined by a short tube 

 with the sac-like vesicula seminalis. F. V. T.] 



There is also a difference in the manner in which Culex and Anopheles deposit 

 their ova. Culex deposits two to three hundred eggs in compact heaps that float 

 on the water, and in which the eggs stand perpendicularly one next the other ; 

 whereas Anopheles maculipennis deposits only three or four up to twenty eggs, 

 united in groups that float horizontally on the water ; the eggs of A. bifurcatus, 

 again, are arranged in star-like groups. The eggs are about 075 mm. in length, 

 and assume a dark hue soon after being laid. The development only occupies a 

 few days. The young larvae grow rapidly, changing their integument several times ; 



FlG. 393. Pupa of Anopheles maculipennis, Meig. 

 Enlarged. (After Grassi.) 



the larvae also differ in the various genera, though they have a general resemblance 

 (figs. 391 and 392). 



The long legless larva has a flattened head, a fairly broad, rectangular, or 

 trapeziform thorax, on which there are bristles, and an abdomen distinctly seg- 

 mented, and on the segments of which there are also lateral bristles. The situation 

 of the stigmata marks the difference between the two genera. Though in both 

 genera the stigmata are at the posterior end and on the dorsal surface, they are in 

 Anopheles close to the surface of the body ; in Culex, however, they are on the free 

 end of a long tube (siphon). 



The position of the larva in the water also differs. The larva of Anopheles lies 

 almost horizontally beneath the surface of the water, the posterior border of the 

 penultimate abdominal segment, upon which the stigmata are situated, being on the 

 surface; whereas the larva of Culex hangs head downwards perpendicularly in the 

 water, the point of the siphon only touching the surface. 



In about a fortnight the larva is fully grown and becomes a pupa. The pupa 



