Cmadiiin mutoinoluijbt. 



Vol. XLV. LONDON, JUNE, 1913 No. G 



NEW NYMPHS OF CANADIAN ODONATA 



BY E. M. WALKER, TORONTO, ONT. 



During the summers of 1907, 1908 and 1912, the writer spent 

 much of his time at the Great Lakes Biological Station, Go Home 

 Bay (Georgian Bay), Ont., in collecting and rearing dragonflies 

 (Odonata). A full account of this work will appear in the forth- 

 coming report of the Marine Biological Stations of Canada; but, 

 as this report will not be issued in the immediate future and is 

 comparatively unknown to entomologists, it is thought best to 

 publish in advance the descriptions of the new nymphs obtained. 



Nymphs of certain species of Aeshna, which were reared for 

 the first time at Go Home Bay, have already been described in the 

 writer's memoir on this genus,* and are omitted from the present 

 account. In addition to the species described from Go Home Bay, 

 the nymph of SomatocJilora semicircular is (Selys) from Vancouver 

 Island is also included. 



Nehalennia gracilis Morse 



A few nymphs of this species were found in floating sphagnum 

 bogs, some distance back from the open water. Several imagoes 

 emerged in the laboratory during July. 



I have compared these nymphs carefully with a few specimens 

 of N. irene (Hagen) from Toronto, and the only differences I can 

 find are the smaller size, less spinulose hind margin of the head and 

 entire absence of spots on the gills. It is not improbable that 

 none of these characters are constant, as I had but few specimens 

 of either species for comparison. 



In N. gracilis the convex posterior margin of the head has only 



4-6 slender inconspicuous colourless spinules; in A^. irene there are 



a dozen or more spinules, which are somewhat coarser and blackish 



at base (Figs. 2, 3) ; gills very slender, widest in the distal third, 



tapering somewhat more gradually than in A'^. irene, with no indi- 



cation of spots (Fig. 1). 



*The North American Dragonflies of the genius /Eshna. University of Tor- 

 onto Studies, Biological Series, No. 11, 1912. 



