208 GENITALIA OF MALE DIPTERA AND MECOPTERA 



The principal features of the genitalia of male insects are the 

 intromittent organ or aedeagus, and the claspers or genital styles 

 (gonostyli), both of which are apparently structures borne on 

 the sternal region of the ninth abdominal segment. In male 

 Ephemerida, the gonostyli or genital styles, labeled ex in figures 

 1 and 4, are borne on a basal plate labeled p, while the intro- 

 mittent organ is made up of a pair of penisvalvae, labeled en. 

 As was pointed out in the article referred to above, the basal 

 plates y of figure 4, may possibly represent the protopodites of a 

 pair of biramous Crustacean limbs, while the genital styles ex 

 may represent the exopodites of such a pair of biramous limbs, 

 and the penis valves en may possibly correspond to the endo- 

 podites of the crustacean limbs. In insects, it is usually the 

 modified limbs and processes of the ninth abdominal segment 

 which make up the genitalia of the malC; and unless this fact is 

 clearly understood, confusion is likely to ensue, since parts of 

 the ninth abdominal segment may be mistaken for the tenth 

 segment, as is the case in the investigations of Berlese, Metcalf, 

 and others. 



In certain ephemerids, the protopodites (coxites) or basal 

 segments of the modified abdominal limbs of the ninth segment, 

 are distinct, and in the ephemerid shown in figure 4, they are 

 represented as partially distinct (i.e. the structures labeled p in 

 figure 4), while in other ephemerids they unite to form a single 

 basal plate (syncoxite), which is borne in the posterior region of 

 the ninth abdominal sternite, and resembles a tenth abdominal 

 sternite so closely that unless one knows its developmental 

 history, he would mistake it for the tenth abdominal sternite. 

 When the protopodites of the limbs of the ninth abdominal 

 segment are distinct, as in certain Lepismatidae and similar 

 forms, they are called coxites. In male sawflics, as for example 

 in the one shown in figure 5, the basal plate labeled sp, which 

 represents the united coxites or protopodites labeled p in figure 4, 

 (i.e. it is a "syncoxite") is called the gonocardo. The genital 

 styles ex of the sawfly shown in figure 5 represent the genital 

 styles (gonostyli) or modified exopodites labeled ex in the ephe- 

 merid shown in figure 4, while the penisvalvae iw of figure 5 

 probably represent the modified cndopodites or the penis valves 

 en of figure 4. Tlu^ genital styles ex of the ephemerids and saw- 



