Proceedings, 1921. 133 



In various parts of Canada we have mosquito problems which in some 

 cases are ahnost as serious as that of New Jersey. In Northern Quebec 

 and Ontario, in areas on the East Coast, on the Prairies, in parts of British 

 Columbia and in the North-west Territories mosquitoes at times assume 

 considerable economic importance. 



The mosquito problem of the Fraser \'alley, British Columbia, is one 

 of the most serious economic factors presented in that district. Agriculture 

 is seriously affected ; at times much of the small fruit is lust owing to the 

 difficulty of obtaining pickers; cattle become very emaciated, and on dairy- 

 farms the drop in milk production is marked during years when mosquitoes 

 are troublesome ; while calves have actually been killed by them. In 

 exceptionally bad seasons lumber camps and mills have been obliged to 

 close down. 



The Dominion Government is undertaking an investigation of the 

 problem, and the writer, under the direction of Dr. C. Gordon Hewitt, the 

 Dominion Entomologist, was engaged during the past summer as a student 

 of the Honorary Research Council in making a preliminary survey of the 

 district and- of the species involved. The following notes are taken from a 

 report to the Dominion Research Council : Nineteen species were taken in 

 the Lower Fraser Valley ; but only two, .ffides aldrichi and .ffides sylvestris, 

 were found to be of any great importance. During years when weather 

 conditions cause the rapid and extended melting of the snow on the 

 mountains the Fraser River overflows its banks and floods the surrounding 

 alder bottoms and open flats. This provides ideal conditions for the 

 extensive development of the two species which are responsible for nearly 

 all the mosquito trouble of the district. 



Some I\Iosquitoes of the Lower Fr.\ser \'.\lley, B.C. 



iEdes aldrichi Dyar and Knab. ' This, the dominant Fraser Delta 

 mosquito, breeds extensively along the river wherever alder bottoms are 

 flooded. This is the first record for Canada, although the species has 

 previously recorded from Idaho and Montana. 



.ffides sylvestris (Theobald) Dyar and Knab. A very common Fraser 

 Valley mosquito. It occurs in great numbers wherever the river floods open 

 flats and meadows. 



JEdes varipalpus Coquillett. A very beautiful black-and-white 

 mosquito which is fairly common in wooded areas. It is a tree-hole breeder, 

 although occasionally larvre may be taken in artificial receptacles. The 

 males as well as the females are attracted to the person, although they 

 cannot bite. 



.ffides punctor Kirby. This is a fairly common but very localized 

 species. It is restricted to woods, especially those that are dark and gloomy. 

 The larvfe breed in shallow temporary woodland pools. 



.ffides cinereus Meigen. This small red-brown species occurs generally 

 throughout the Fraser \'alley. Although at times they bite viciously, they 

 are seldom troublesome and never leave the vicinity of their breeding-places. 

 The larvje are found in shallow, protected surface pools and alder-swamps. 



