40 



The species are numerous and difficult of separation. The 

 nymphs are not usually abundant, and as few of even the com- 

 moner American species have been bred, our knowledge of the 

 immature stages is as yet unusually imperfect. The key which 

 follows indicates the salient characters of the nymphs here 

 treated. In the young nymphs of yEsvlnia sp. h a tendency to 

 abdominal cross-bands was noted, and the sutures beneath 

 were broadly bordered with paler color, except those between 

 3 and 4, 6 and 7, and S and 9. 



KEY TO THE NYMPHS OF ^SCHNA HERE DESCRIBED. 



act. Lateral spines of sixth abdominal well developed, reaching 

 at least about half way to the hind margin of the seg- 

 ment; those of seventh attaining about to the hind 

 margin; lateral labial lobes squarely truncate at tip. 

 hh. Fifth abdominal with minute lateral spines, lateral 

 appendages fully two thirds as long as the superior 

 appendage; supracoxal processes sharp, equal. 



1. clepsijdra. 

 h. Fifth abdominal with at most only a trace of lateral 

 spines; lateral appendages less than two thirds as 

 long as the superior; supracoxal processes less sharp, 

 the posterior larger; abdomen in younger individ- 

 uals with a medio-dorsal pale line bordered each 

 side with blackish. 2. eonstricfa. 



a. Lateral spines of sixth abdominal minute, distant from its 

 hind margin by several times their own length, those 

 of seventh reaching about half way to the hind margin. 

 cc. Apices of lateral labial lobes squarely truncate, con- 

 tiguous when closed; in younger specimens a pale 

 spot near anterior ocellus and another on clypeus, 

 and a pale median line enlarged on the middle 

 of abdomen into an increasing series of pale spots, 

 the largest and last on segment seven. 

 (hi. Superior appendage sparsely fringed laterally with 

 pale hairs; posterior part of head with some pale 



