THE CANADIAN ENTOMOLOGIST 415 * 



• 1 



In Sympetrum it is usually but little longer than broad, and falls 

 considerably short of the inferior appendages even when the ap- 

 pendages are closed together. The head in Sympetrum is relatively 

 somewhat larger, as a rule, than in Leucorrhinia. 



Leucorrhinia hudsonica and L. horealis are distinguishable 

 from all the known nymphs of Sympetrum except S. ruhicundulum, 

 S. illotum and S. corruptum by the absence of dorsal hooks on segs. 

 7 and 8. They are readily separated from these by the much 

 larger lateral spines and the conspicuously striped venter of the 

 abdomen. The other species of Leucorrhinia are distinguished 

 from Sympetrum by the presence of a small dorsal hook on seg. 3, 

 which, however, is very minute in L. proxima. 



In offering the following key I am well aware that it may prove 

 unsatisfactory in certain respects. The nymphs of Leucorrhinia 

 and Sympetrum are variable in the very characters which are 

 most useful in separating them. Those of L. intacta, glacialis and 

 proxima are extremely similar and as I have had only a single 

 exuvia of glacialis and but two of proxima it is quite uncertain 

 whether or not the characters given will prove to be constant 

 when more material is available for study. 



Key to the Nymphs of the North American Species of 



Leucorrhinia. 

 A. Dorsal hooks present on abd. segs. 2-8, venter of abdomen 

 without longitudinal dark bands. 



B. Eyes very prominent; lateral spines of seg. 9 extending 

 back nearly or quite as far as tips of inferior 



appendages .frigida Hag. 



BB. Eyes less prominent, lateral spines of seg. 9 not extend- 

 ing back as far as tips of inferior appendages. 

 C. Dorsal hook of seg. 7 as long as mid-dorsal length of the 

 segment, that of seg. 8 projecting well over the base 

 of seg. 9; lateral spines of seg. 8 more or less divergent, 

 their outer margins not continuing the regular curve of 

 the abdominal margin ; lateral spines of seg. 9 extend- 

 ing beyond tips of lateral appendages. 

 D.Spinuleson inner margin of lateral lobes of labium 

 mostly in groups of 3; lateral setae 10; dorsal hook 



