80 THE CANADIAN ENTOMOLOGIST 



usual. While an occasional thaw came in direct contact with the 

 surface, thus providing a thawing and freezing condition known 

 to be detrimental to insect life, there is no doubt that several species 

 suffered in consequence, but the Colorado Potato Beetle, as a rule, 

 burrows sufficiently deeply to escape the thawing effect, hence frost 

 alone was to be reckoned with. 



The result of this lack of snow was very marked the following 

 May. Beetles which had gone into winter quarters in a healthy 

 condition were found huddled together in a state of death, not a 

 single living example being located in the more exposed situations, 

 though later in the season odd individuals turned up on potato 

 plants forming the nucleus for future generations. The country was 

 by no means all affected in the same way; some parts had a light 

 covering, others a foot or more. Consequently the amount of 

 snow necessary for protection could be ascertained with reasonable 

 accuracy. As was mentioned above, complete lack of snow, or less 

 than three inches, did not afford sufficient covering for the beetles. 

 the few survivors having probably sought shelter beneath some 

 straw or brush pile. Where there was a depth of snow amounting 

 to from four to six inches the survivors were considerably increased. 

 At eight inches about half the beetles survived, while a foot or more 

 of snow apparently produced complete immunity from frost. 



In the vicinity of the Entomological Laboratory at Treesbank 

 very few beetles escaped, which proved a great boon to potato 

 growers. The effect of this winter killing is still very marked 

 (1916), less than one per cent, of the plants being infected. Near 

 Winnipeg, on the other hand, where the snow fall was ample no 

 mortality was noticeable among the beetles, and they have con- 

 tinued'to be a serious pest there. 



From the above account it is evident that snow plays an im- 

 portant part in the preservation of animal life, it also saves many a 

 garden plant from destruction. Under normal conditions it will 

 continue to afford protection to the Colorado Potato Beetle, but 

 we can at least see that there will be years of severe check, like the 

 winter of 1914-15. \A'hile there is every reason to believe that 

 those portions of the country where snowfall is light will never prove 

 a prolific breeding ground for that insect. 



