88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 95 



of the ninth sternum may form but a rounded Hp beneath the geni- 

 tal opening, or gonotreme, above it (B), or it may be produced 

 into a subgenital lobe of varying length (I, K, M), which in some 

 forms is differentiated from the rest of the sternum by a weaker 

 sclerotization (K). 



The tenth segment is always a distinct annulus, though it varies 

 in form and size and in the relative development of its sclerotized 

 areas. In some species the tergum of the tenth segment is a large 

 plate covering the back and sides (fig. 29, A, D, G, XT), whereas 

 the venter is unsclerotized (B, D, I) and may appear as a membranous 

 fold behind the gonotreme (B, X.V). In others the reverse occurs, 

 a large sternal plate being the principal sclerite of the tenth segment 

 (L, M, XS) ; or again, both the tergum and the sternum may be 

 confluent in a continuously sclerotized ring (J, K, X). The armature 

 of the tenth segment consists most commonly of lateral lobes or 

 hooklike processes produced upward from the posterior margins 

 (F, ^) ; but in Luectra, as already described, the sternum of the seg- 

 ment bears a group of processes arising just behind the genital orifice 

 (M, /, g). By the upward curvature of the end of the abdomen the 

 tenth segment may be inverted (L, XS), and the sternal processes 

 then project dorsally and anteriorly. In some forms a short process 

 arises from the posterior margin of the tenth sternum. 



The eleventh segment consists of the usual epiproct and paraprocts 

 (fig. 29 A, Eppt, Papt), with the cerci {Cer) arising at the bases of 

 the latter. The circi are typically long, slender, multiarticulate appen- 

 dages, but in the Nemouridae they are reduced, those of the male in 

 most cases consisting of a single " segment" (G, I, K, L, M, Cer). 

 The armature of the eleventh segment includes a pair of processes 

 borne by the paraprocts, and a median process of the epiproct, though 

 either or both may be absent. The paraproctial processes arise from 

 the upper surfaces of the paraprocts and project dorsally. They com- 

 monly have the form of a pair of hooks (A, D, h), but they may take 

 on more complex shapes (G, I, h). They are said to be used by the 

 male for depressing the subgenital plate of the female. In the mating 

 position the male rests upon the back of the female, and, in the man- 

 ner of a grasshopper, lowers his abdomen on one side of that of the 

 female and turns the end upward beneath the genital region of the 

 female (see description by Hagen, 1877, figure by Wu, 1923). The 

 everted or protracted phallus projects upward and forward, its end 

 presumably being inserted into the female genital chamber. 



The median process of the epiproct is variously developed, often 

 attaining a large size and complex structure (fig. 29 G, J, K, i). It 



