1913] 



Biology of May-flies. 



395 



External Genitalia of the Male. 

 The external genitalia of the male consists of a pair of 

 forceps, jointed except in Csenis and Campsurus, and two 

 penes, each with a distinct opening. The forceps are incurved 

 appendages of the tenth segment, by which the male grasps 

 the abdomen of the female. The genitalia of Hexagenia 



Fig. 3. A, external genitalia of Hexagenia sp.? cf; p, penis; o. s. d., 

 ■opening of seminal duct; f, forceps. B, ventral view of rear abdomen of Hexa- 

 genia sp.? 9, showing ov, outline of oviduct seen through body-wall; o. 6v., 

 opening of oviduct; e. v., egg-valve; 7, 8, 7th and 8th sternites. 



sp.?* are of the simple type. The forceps are three 

 jointed, with a stout basal piece. The two distal seg- 

 ments are concave on the inner surface and tip. These con- 

 cavities, the flap like extension upon the main segment and 

 the inner surface of the basal piece are thickly covered with 

 small papillae, which are characteristic of nearly all forceps ex- 

 amined. The roughened surface produced by them probably 



This is a species Hexagenia recurrata in manuscript which I have to be pub- 

 lished. 



