13 INSECUTOR INSCITI^ MENSTRUUS 



tory, July 21, 27, 1919; White Horse, Yukon Territory, June 

 27, 28, July 1-4, 9, 14, 18, 1919; Tahkeena River, Yukon 

 Territory, July 19, 1919 ; Hootalinqua, Yukon Territory, July 

 15, 1919 ; Tantalus Mine, Yukon Territory, July 6, 1919 ; Big 

 Salmon, Yukon Territory, July 15, 1919 ; Carmack's, Yukon 

 Territory, July 14, 1919 ; Dawson, Yukon Territory, July 7-13, 

 15-17, 19, 1919. 



Aedes excrucians Walker. 



A male was demonstrated from White Horse, Yukon Terri- 

 tory. In the west this species is much less common than fitchii. 

 Larvae from Prince George, British Columbia, have the air- 

 tube somewhat shorter and stouter than in those from Massa- 

 chusetts ; but the detached pecten-teeth, comb-scales and head- 

 hairs are the same. 



The name sansoni D. & K. is available for the western form, 

 but I think a separate name is unnecessary as there are prac- 

 tically no differences. 



Aedes stimulans Walker. 



Culex stimulans Walker, List Dipt. Brit. Mus., i, 4, 1848. 

 Culex cantons Theobold (not Meigen), Mon. Culic, i, 401, 1901. 

 Culicada subcantans Felt, Bull. 97, N. Y. Sta. Mus., 448, 1905. 

 Culex (Culicada) stin;,ulans Speiser, Schr. Phys.-okon. Ges. zu 

 Konigsb., xlix, 391, 1908. 



The preferred habitat of stimulans larvae in the east is pools 

 which have been actually overflowed by early high water, not 

 seepage-filled. Such pools are common along streams in the 

 Atlantic water-shed where the valleys are broad and low. In 

 western Canada, however, the streams are deeply cut, with 

 steep banks, for example the Saskatchewan or the Bow, and 

 pools of this character do not occur. It has thus been neces- 

 sary for stimulans to cease to exist in the west or change its 

 habits. In writing the monograph, we were of the opinion 

 that the species adopted the former alternative, as we state 

 (vol. iv, p. 682) : it "does not seem to be represented in the 

 far west by an allied form." However, I have found it at 

 Edmonton, Alberta, breeding in early marsh-pools with decticiis 



