182 Journal New York Entomological Society. [Voi. xi. 



Ptychoptera !enis O. S. (PL XI, Fig. 20.) 



Considerably different from any others examined. The abdomen 

 is club-shaped, enlarging posteriorly to the seventh segment. The 

 eighth, ninth and tenth terga are consolidated and covered by the 

 posterior margin of the seventh. The eighth sternum is short and 

 thick and its appendages {a) are rudimentary. The cerci {cer), on 

 the other hand, are extremely large plates widest near the middle, 

 tapering to a point distally. 

 Ctenophora bimaculata, C. flaviolata, C. angustipennis. 



Parts all of ordinary form. In C. atrata the tip of the abdomen 

 and the cerci are greatly prolonged and tapering. 

 Pachyrrhina, spp. 



Eight species were examined and none were found to depart from 

 the ordinary type. 



This study of the female abdomen shows that there is but one type 

 of structure throughout the entire family, and that the generic and 

 specific modifications of this type are but slight. The contrast be- 

 tween the males and the females in this respect is very striking. The 

 modifications of the female parts are insignificant when compared with 

 the enormous variety of hypopygial structure in the males. It is 

 utterly impossible to point out any correlation between the variations 

 of the corresponding parts in the two sexes. There consequently 

 arises the interesting problem of explaining the modifications of the 

 male genital parts by some other theory than that of adaptation to the 

 female organs. 



EXPLANATION OF THE PLATES. 



a, appendages of eighth sternum ; cer, cercus ; gon. 2, second gonapophyses ; 

 FIJI t, eighth tergum ; VIII s, eighth sternum; IX, X, ninth and tenth terga. 



Plate X. 

 Fig. I. Tipula bicornis, lateral view of end of abdomen. 



Fig. 2. Tipida angustipennis, second gonapophyses (^gon. 2) and lower ends 

 of ninth tergum ( IX t. ) . 



Fig. 3. Tipula retusa, lateral view of end of abdomen. 

 Fig. 4. Tipula unicincta, ninth sternum. 



Fig. 5. Tipula angustipennis, lateral view of end of abdomen. 

 Fig. 6. Tipula bella, ninth sternum and lower ends of tergum. 

 Fig. 7. Tipula angustipennis, ventral view of end of abdomen. 

 Fig. 8. Tipula angustipennis, fused first gonapophyses. 

 Fig. 9. Tipula angustipennis, dorsal view of end of abdomen. 

 Fig. 10. Tipula angustipennis, lateral view of entire abdomen. 



