THE CANADIAN ENTOMOLOGIST 



373 



Aeshna palmata. 



Aeshna umbrosa. 



Georg. Bay (reared) 



Toronto 



Toronto 



Toronto 



Georg. Bay (reared) 

 Vane. I. (reared) . . . 



Average 



2.8 

 2.8 

 2.6 



2.73 



It will be seen that the length of the hind femora and of the 

 mentum of the labium is about the same in the two species, but 

 that in the other measurements, particularly the length of the 

 ovipositor, palmata has somewhat the advantage. The measure- 

 ments of segment 3 are less reliable than those of segments 7 and 9, 

 as the form of this segment varies considerably in the exuviae. 



Ecologically there is quite a marked difference between these 

 species. Umbrosa is everywhere an inhabitant of small streams, 

 while palmata lives in pools and small ponds. I found nymphs of 

 umbrosa associated with those of Cordidegaster dorsalis in a small 

 forest brook near the Biological Station on Vancouver Island, 

 palmata being entirely absent from this stream. About two miles 

 from this spot was a small pool in the woods, grown up with western 

 Skunk Cabbage. This pool contained numerous nymphs of 

 palmata, but no other Aeshna. 



Sympetrum pallipes Hagen. 

 We found this species in abundance on Vancouver Island 



