10 



Annals Entomological Society of America [Vol. XV, 



they seem to be characteristic of a very primitive type of 

 genitaHa, they are probably structures of ancient origin, whose 

 representatives we should expect to find in the Thysanura. 

 It seems best, therefore, not to distinguish these structures by 

 different terms until further light is thrown upon their origin. 



Fig. 3 



Fig. 3. Ventral views of terminal abdominal segments, illustrating homologies 

 of male and female structures (semi-diagrammatic), a, Machilis, male; 

 b, hypothetical Pterygote type male; c, Ephemerid male; d, Grylloblatta, 

 immature male; e, Blattid, male, based on Periplaneta; i, Tettigoniid immature 

 male of Neoconocephaliis; g, Machilis, female; h, hypothetical Pterygote 

 type, female; i, Grylloblatta, immature female; j, Blattid, immature female of 

 Parcoblatta; vd, dorsal valvulae; vi, inner valvulse; vv, ventral valvulae. 

 For other lettering, see page 71. 



