410 THE CANADIAN ENTOMOLOGIST 



moderately to decidedly prominent; lateral margins very oblique, 

 curving into the straight, posterior margin with no indication of 

 an angle. Labium reaching caudad to the middle coxae, scarcely 

 longer than broad, the middle lobe obtusangulate, mental setse 

 usually 13 to 15, lateral setae usually 9-11 but sometimes more, 

 inner margins of lateral lobes with very low crenulations, the 

 marginal spinules in groups of 2 to 4, of which one is much the 

 longest, movable hook slender, rarely more than half the length 

 of the lateral margin. Abdomen ovate, but little depressed, 

 broadest at segment 6, narrowed more abruptly caudad than 

 cephalad; dorsal hooks never present on segs. 1 to 3 nor on 9 and 

 10, usually shorter than the segments which bear them; lateral 

 spines on segments 8 and 9 or on 9 only, generally shorter than 

 their respective segments; superior appendage triangular, but 

 little longer than broad, acuminate, with a very slender pointed 

 apex, lateral appendages about half as long as inferior appendages, 

 the latter generally acuminate, fine-pointed and decidedly longer 

 than the superior appendage. 



The nymphs of Sympetrum are very like those of Leucorrhinia, 

 and there seem to be no good characters for separating them 

 generically. (See Can. Ent., 1916, vol. XLVIII, p. 414.) 



Key to the Nymphs of North American Species of 



Sympetrum. 



1. Segs. 8 and 9 with lateral spines, dorsal hooks present (except 



in some individuals of S. ruhicundulum decisum) 2 



Seg. 8 without lateral spines, those of seg. 9 vestigial, dorsal 

 hooks entirely absent ...8 



2. Dorsal hooks on segs 6-8 as long as the segments which bear 



them, lateral spines of segs. 8 and 9 subparallel, those of 

 seg. 9 as long as the lateral margins of the segment (not 

 including spine) and reaching back as far as tip of superior 



appendage; eyes prominent 3 



Dorsal hooks shorter than the segments which bear them; 

 lateral spines more or less convergent, their outer margins 

 continuing the general curve of the abdominal margins; 

 those of seg. 9 shorter than the lateral margins of the seg- 



