372 THE CANADIAN ENTOMOLOGIST 



yEshna palmata Hagen. 



During the summer of 1913 I reared a number of specimens of 



this species and obtained a large number of exuviae. A study of 



this material shows that the two exuviae referred to this species in 

 my "North American Dragonflies of the Genus Aeshna" were 

 correctly placed, but that some of the characters used to separate 

 it from A. umbrosa are not valid. 



I now possess a large series of exuviae of both species, including 

 several of umbrosa from Vancouver Island, where most of my 

 nymphs of palmata were taken. I find that the two species at 

 this stage are so much alike that in many cases it is a difficult 

 matter to separate them with certainty. The form of the living 

 nymph is probably invariably stouter in palmata, but this difference 

 is often difficult to detect in preserved material, though usually 

 evident enough, to the trained eye, in the exuviae. The difference 

 in the form of the labium is often but slight, but it seems to be 

 always- slightly broader at base in palmata. The absence of an 

 internal apical tooth on the lateral lobes, employed by me as a 

 differential character for this species (N. Am. Aeshna, pp. 68, 162), 

 is a mere individual variation. The tooth is normally present as 

 in umbrosa. The differential based upon the supra-coxal processes 

 seems to be constant and is certainly a useful character. The 

 posterior process is always the stouter and often the longer in 

 umbrosa, while in palmata they are equal or very nearly so, the 

 anterior being sometimes the larger (pi. XXV, figs. 4-5). 



The ovipositor is slightly larger in palmata and extends slightly 

 beyond the hind margin of segment 9, but seldom covers as much as 

 one-third of segment 10 as given in the key. In umbrosa it just 

 reaches the margin. 



These differences in Avidth of labium and abdominal segments 

 and in length of ovipositor will be best appreciated by referring to 

 the following table, which is based upon three males and three 

 females of each species, taken at random. The first three of each 

 species are males. The length of these specimens is nearly the 

 same throughout the series. The relative size is roughly indicated 

 by the lengths of the hind femora. 



