274 A7inals Entomological Society of America [Vol. XII, 



Part I. The Terminal Abdominal Structures 



OF THE Female, 



The female external genitalia of a typical generalized 

 Pterygote insect (e. g., Ceuthophilus, Figs. 1-4), consist of 

 the vulva or genital aperture, situated at or near the posterior 

 end of the eighth abdominal sternum' and usually protected 

 by a backward prolongation of the latter (in some cases the 

 seventh sternum), the subgenital plate (st. 8); and three pairs 

 of processes, the gonapophyses or valvules, which co-operate to 

 form the ovipositor. These valvule are distinguished, from 

 their usual positions, as the ventral, dorsal and in?ier valvtdce 

 (valves) or the anterior, lateral and posterior gonapophyses, 

 respectively. The ventral valvulas arise primitively from the 

 posterior margin of the eighth sternum, though often actually 

 from the intersternal membrane between segments eight and 

 nine; the dorsal and inner valvulas from the ninth sternum, 

 primitively also from the posterior margin. 



The ventral, valvulae (vv) consist of a shorter basal segment, 

 the hasivalviila (Crampton, '17)^° and a longer shaft. The 

 basivalvula (bs) is usually chitinized only ventrally or ventro- 

 laterally, if at all, the shaft externally, when a functional 

 structure, but becoming partly or entirely membranous when 

 the ovipositor is degenera'^e. 



The dorsal valvulas (vd) may be more or less distinctly 

 separable into a broad proximal portion and a longer, more 

 slender distal part, but there is no line of demarcation between 

 these parts and nothing comparable to the basivalvulae ; the 

 parts so designated by Crampton being in some cases the 

 lateral part of the ninth sternum (or valvifer, vide inf.y^', in 

 other cases merely the basal part of the valvula itself,^- the 

 appearance of a suture being due to parts beneath showing 

 through the valve. 



The inner valvulae (vi) are enclosed by the other two pairs 

 and are usually the shortest pair. They commonly enclose 

 or roof over, the passage through which the eggs are passed out 



10 Crampton, Journ. X. Y. Ent. Soc, Vol. XXV. p. 2.36 (1917). Also termed 

 "Basalstiick" (Van der Weele, Tijd. voor Ent., Deel XLIX, pp. 99-198, Pis. 1-3, 

 1906), and '-basal plate" (Walker, Univ. of Toronto Studies, Biol. Scr., No. 11, 

 1912). 



" Crampton, op. cit., PI. XVI, Fig. 7; PI. XVII, Fig. 12. 



12 Crampton, op. cit., PI. XVI, Figs. 1, 6; PI. XVII, Fig. 10. 



