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BIOLOGICAL SOCIETY OF WASHINGTON. 



to reach with her head to the extreme lower end of her follicle, 

 causing, in doing so, the narrow elastic portion of the follicle to 

 bulge, and the orifice to open more or less, as it repeatedly did 

 while the larva was yet feeding, whenever the excrement had to be 

 expelled. Fig. 2, a, shows a follicle cut open so as to exhibit the 

 elongated puparium, and the female extended from it as she awaits 

 the male ; b, represents this degraded female more in detail. A 

 cursory examination of the male shows the genital armature, which 

 is always exposed, to consist of (i ) a brown, horny, bilobed piece, 

 broadening about the middle, narrowing to and notched at tip, con- 

 cave, and furnished with a tuft of dark hairs at tip inside] (2,) a 

 rigid brown sheath, upon which play (3) the genital hooks or 

 clasps, which are also concave inside, strongly bifid at tip, the 

 inner finger furnished with hairs, the outer produced to an obtuse 

 angle near tip, and generally unarmed, (Fig. 3, e). In repose, this 



Fig. 3. Thyridoptervx ephemer.-eformis: b, the end of male abdomen 

 from the side, showing genitalia extended; <r, genitalia in repose, ventral view; 

 d, do., dorsal view ; e, tip of bifid clasp ; /, tip of penis ; all enlarged. 



armature appears as in Fig. 3, c, from beneath, and as at d, from 

 above, and is well adapted to prying into the opening of the folli- 

 cle. The male abdomen is telescopically extensile, while the tip 

 easily bends or curves in any direction, but most naturally beneath, 

 as at b, where it is represented enlarged about six times, and with 



