1920] Crampton — Genitalia of Male Hymenoptera and Other Insects 35 



male of the interesting insect Gryllohlatta campodeiformis, has made 

 it possible to revise the interpretation of the parts in the higher 

 forms, in the light of the increased knowledge of the subject, 

 gained from these sources. 



For the purpose of the present paper, it is sufficient to begin 

 the study of the modifications met with in the higher forms with a 

 consideration of the condition exhibited by the primitive mayfly 

 Blastunis cupidus (Fig. 11). The sternite of the ninth abdominal 

 segment in this insect (labeled "ha" in Fig. 11, Plate IV) bears 

 a pair of somewhat closely united, plate-like sclerites, called the 

 styligers or "coxites," one of which is seen in profile in Fig. 11, 

 where it bears the label "p." Dr. Walker correctly compares these 

 styligers or "coxites" with the basal segments of abdominal limbs 

 (protopodites ?) retained in such lower insects as Machilis, in 

 which the styligers or "coxites" bear styli which are possibly 

 homologous with the exopodites (or epipodites ?) of crustacean 

 limbs. Similarly, in Blasturus, the styligers or "coxites" labeled 

 "p" in Fig. 11, bear styli "s"; but in the latter insect, there are 

 traces of two segments in the styli (and in some mayflies there 

 are three or more segments in the styli), while the styli of most 

 apterygotan insects are composed of but one segment. The seg- 

 mented styli of ephemerids ("s" of Fig. 11) are called gonopods, 

 gonostyli, or arthrostyli. Following Morgan, 1913, Eaton (Mono- 

 graph of the Ephemerida), Berlese, 1909, and others who have 

 figured the parts of male ephemerids, I formerly interpreted the 

 plates "p" of Fig. 11 as representing the sternite of the tenth 

 segment; but they are apparently structures belonging to the 

 ninth segment, as pointed out above. In this connection, it 

 should be noted that the designation- " tenth segment" refers to 

 the tenth abdominal segment, not including the three thoracic 

 segments in the count, as is usually done by lepidopterists. 

 Furthermore, it should be borne in mind that the actual first 

 abdomnial sternite has become atrophied in most insects, and the 

 first apparent sternite really represents the sternite of the second 

 abdominal segment, so that it is preferable to count the segments 

 on the dorsal side, where most of them are preserved in the lower 

 forms. 



Palmen, 1884 (page 42) in describing the development of the 

 vasa deferentia of mayflies, states that they extend to the posterior 



