68 



SCIENTIFIC AGRICULTURE 



Fehniarv, 1921. 



Mosquito Control Investigations In British Columbia 



By ERIC HEARLE, Entoiii(,looic;il Biandi. Ottawa. 



It is hard for those who live where mosquitoes are 

 not abundant to realize the iueomparable misery caus- 

 ed by the attacks of hordes of the winged plagues in 

 less fortunate districts. In many parts of America the 

 topograpliy and local conditions are not suitable for 

 the production of an abundance of mos(|uitoes; but in 

 other places where low undrabied areas subject to 

 flooding by rain, tides or freshets occur, mosquitoes 

 nuay he produced in such enormous numbers that they 

 rank foremost among the enemies of man. In New 

 Jerse.y, for instance, the huge salt marshes, wliich are 

 flooded by tlie liigh tides, produce enormous numbers 

 of mosquitoes, whose importance can be gauged from 

 the following extract from the 1917 Report of the 

 Department of Conservation and Development of New 

 Jerse.v. The Boai'd "is convinced tliat tlie salt marsh 

 mosquitoes, more than anything or tlian all else, arc 

 responsible for the backwardness of the Eastern and 

 Southern sections of the State. The,v have depopulated 

 farms, prevented the gro^vth of to\^Tis, hampered the 

 development of shore resorts and restricted the exten- 

 sion of suburban communities." A very careful study 

 of New Jersey's mosquito problem has sliown that mos- 

 (juito control is feasible even when very large areas 

 are affected ; and the adoption of the control measures 

 suitable to New Jersey, indicated by the investigations 

 of J. B. Smith and T. J. Headlee, has very greatly 

 mitigated tlie pest wherever the work has l)een effici- 

 ently carried out. 



In Canada mosquitoes are sufficiently abundant in 

 places to be of very great importance. Investigation 

 of some of these places is now under way and it is be- 

 lieved that the application of suitable control measures 

 will result in a great reduction of the financial losses 

 caused by mosquitoes, which losses in the aggregate 

 amount to many thousands of dollars, to say nothing 

 of making life infinitely more pleasant for those living 

 in the affected areas. 



The Eraser Valley, Britisli Columbia, is one of the 

 l)laces periodically subjected to infestation by liordes 

 of mosquitoes. This occurs during the period of greatest 

 outdoor activit.y and absolutely takes all jileasure from 

 life during the summer — the best season of the vear. 



.y.ii^iyyMiMyi 



l'l(iM,lpil lioihim lands— Tlio cliiof smiv 

 Fiasei- Valley. B.C. 



fif mri.«!riii!fneq. 



I'ld.iil.ii lui-aduw — The breetling- place of Aedes vexans. 



The Entomological Brancli of the Dominion Depart- 

 ment of Agriculture, in resjionse to a request from the 

 residents of the district, has for the last two years un- 

 dertaken an investigation of the problem. During the 

 first year a faunal survey was made, and, by means of 

 an automobile over two thousand S(|uare miles of terri- 

 tory were scouted for adult and larval mos(|uitoes. The 

 mosquito fauna, consisting of over twenty species, was 

 studied as to abundance, migration, virulence of 

 poison, larval habitats, etc., and the import)ant mos- 

 quitoes were found to be of two species which breed 

 in the low areas bordering the Fraser river, whenever 

 these are flooded by the sjiring freshets. The other 

 species are of slight importance, either because they do 

 not occur very abundantly, or, in some eases, because 

 they have very poorly developed predatory instincts. 

 During the -past season a motor boat and canoe were 

 utilized to make a careful study of the main problem 

 and the work was largely restricted to surveys of the 

 river-flood breeding places. 



Tjie dominant species in the district is " Affh.'i nl- 

 drichl'' Dyav, a masquito previously known only from 

 Idaho and Montana. The larva was unkno^m until the 

 writer found it last year, and as yet comparatively 

 little is knowni of its life-history. The winter is passed 

 in the egg-stage in the alder-bottom areas bordering 

 the river. At the spring freshets extensive flood-pools 

 are formed in these places and enormous numbers of 

 mosquitoes are produced. The adults are callable of 

 spreading over areas as far as fifteen miles from the 

 breeding places. Although this species bites worst at 

 dusk it is extremely troublesome in sheltered places all 

 through tlie day and it is especially bad in berry 

 patches. This mosquito is very small and is sage-grey 

 in color: the legs are dark and unbanded ; tlie aiido- 

 miiial segments have basal white bands; and the thorax 

 is (iniaiiiented witli a divided browii stripe. 



The other important mosquito in !the district is 

 "Aedfst vesfins" Meigen, a dusty browni species with 

 very marked constrictions in the white abdominal 

 bands, somewhat indistinct narrow rings on the tarsal 

 segments, and an unoriiamcntc<l biowii thora.x. The 



