58 The Ottawa Naturalist. [June 



These specimens all belong to the variety called semiaquea 

 in which the black patch at the base of the hind wings reaches 

 beyond the triangle, sometimes as far as the nodus. The 

 typical cynosura is found at Toronto with semiaquea, but the 

 latter seems to be the only form found in the north. It is 

 exceedingly abundant there, however, occuring in myriads about 

 all the lakes and larger streams during June and July. It is an 

 insect of splendid aerial powers and on sunny days is seldom seen 

 to rest. 



The males of this species may be separated from those of 

 T. spinigera and T. cants by the absence of spines from the 

 superior appendages. 



37. Tetragoneuria spinigera (Selys) Selys. 

 1 male, 1 female (Maclaughlin). 



This species is generallv larger than cynosura, and has 

 very little black at the base of the hind wings. The superior 

 appendages of the male bear a small inferior spine. 



It is common in the northern parts of Ontario. 



38. Tetragoneuria canis Maclaughlin Figs. i3, i4. 

 Ottawa, 1 male (Harrington); Chelsea Road, Ottawa, Mav 



27th, 1886, (Fletcher); Hull, June 2nd and 7th, 1Q03. 3 males 

 (Harrington). 



These are the only Canadian specimens I have seen of this 

 species. The males may be known by the form of the superior 

 appendages, which are curved downwards and bear a stout 

 dorsal spine. 



This species was recorded by me in the Entomological 

 Record, Ann. Rep. Ent. Soc. of Ont., 1906, as T. spinosa, Selys, 

 a closely allied species with which it has apparently been con- 

 founded by several writers. The determination T. canis was 

 confirmed by Dr. Calvert. 



Genus Helocordulja, Needham. 



39. Helocordulia uhleri (Selvs), Needham. Figs. 15, 

 16. 



Buckingham, P.Q., May 31st, 1 female (Fletcher). 



A rather small Corduline (abd. 29 mm.), olivaceous with a 

 blackish abdomen. Hind wings with a black spot at base extend- 

 ing as far as the first antecubital. Just beyond this is a yellow 

 spot and a few small black ones marking some of the ante- 

 cubitals. 



This dragonfly, which appears in early summer, will probably 

 prove to be fairly common about the lakes and streams of the 

 Laurentian area. 



Genus Dorocordulia, Needham. 



