NO. 8 ANATOMICAL LIFE OF THE MOSQUITO — SNODGRASS 69 



The male mosquito is readily distinguished from the female by the 

 presence of a pair of large, two-segmented genital claspers, or 

 paramcres, projecting from the end of the abdomen (fig. 27 A, Pmr). 

 Though the ninth segment is ordinarily concealed by retraction into 

 the eighth, on pulling out the end of the abdomen (B), it is seen to 

 be a small sclerotic ring (IX) carrying the parameres. The anus- 

 bearing tenth segment, or proctiger (X), is mostly hidden between 

 the bases of the parameres, and is apparently ventral in position. In 

 fact, the whole terminal part of the male abdomen beyond the seventh 

 segment, except in newly emerged individuals, is turned upside down, 

 so that the tergal plates are ventral and the sternal plates dorsal. The 

 inversion takes place slowly during the first 24 to 48 hours after 

 emergence from the pupa. 



The tenth abdominal segment of the male is a flattened anal lobe 

 with an expanded base projecting from above the inverted tergum of 

 the ninth segment (fig. 27E,F). In its base are two dorsolateral 

 sclerites (t) that may be regarded as tergites. On the ventral (upper) 

 surface are two marginal bars (s), the ends of which project as a 

 pair of free, toothed prongs. These bars have commonly been re- 

 garded as sternites, but Christophers (1923) says they are the cerci 

 united with the anal lobe. 



The external genital organs of the male insect, because of their 

 generic and specific variations, are important diagnostic features for 

 taxonomists. In the mosquito they include primarily the paired lateral 

 claspers and a median intromittent organ, carried by the ninth ab- 

 dominal segment. Various names are given to these parts by different 

 specialists, but the organs have essentially the same origin in all insects, 

 and there is no need for special terms in the several orders, and 

 certainly there is no excuse for specialists in one order to use different 

 names for the same parts in different species. For simplicity the 

 claspers are here termed the parameres, and the intromittent organ 

 the aedeagus. Various secondarily developed accessory parts, of 

 course, must have more specific names. 



In the insects in general the male genitalia take their origin from 

 a pair of primary phallic lobes that develop in a late instar of the 

 nymph or larva on the posterior part of the ninth abdominal segment 

 at the sides of the future gonopore. Later, each lobe divides into two 

 parts, a mesal mesomere and a lateral paramere. Eventually the 

 mesomeres unite around the gonopore to form the aedeagus, and the 

 parameres become the claspers. 



The development of the genital organs in the male mosquito has 

 been shown by Christophers (1922) to proceed in the usual manner. 



