%\\t Canadian |IutomoIo0i3t. 



Vol. XLIX. LONDON, AIARCH, 1917 No. 3 



POPULAR AND PRACTICAL ENTOMOLOGY. 



Precipitation' ix Relation to Insect Prevalence and 



Distribution. 



by nur.man criddle, dominion entomological labor.\tory, 



TREESBANK, MANITOBA. 



In this paper an attempt is made to draw attention to a few 

 instances of how humidity, chiefly in the form of rain or snow, has 

 been and is instrumental in either aiding or curtailing the spread 

 of insects over the country, particularly in the Prairie Provinces. 



There are very few insects, if any, that can live through all their 

 stages without the aid of moisture. Most of them, indeed, are very 

 much dependent upon it, especially in their larval stages. Numer- 

 ous examples could be given, and a suitable one is provided in the 

 various races of Tiger Beetles (Cicindela). We find these beetles 

 from haunts in close proximity to water, to habitations on plains 

 of drifting sand, apparently far removed from it; yet an examina- 

 tion a few inches below the surface, in the latter place, will show that 

 the sand, if not equally moist, is at least sufficiently so for the wants 

 of the beetle larvae, which are easily able to burrow down to it. 

 There are occasions, however, when the insects' prairie haunts be- 

 come very dry; at such times there is reason to believe that some 

 of the larvae perish while the remainder retire to the bottom of their 

 burrows and remain inactive until such time as rain once more 

 moistens the soil. 



While most insects require water in some form or other, there 

 are certain kinds which seem to thrive best when it is least prevalent, 

 and are only found in the dryest situation. In this class we have 

 most of our locust pests, and the celebrated Rocky Mountain 

 Locust {Melanoplus spretis) supplies a good example. This locust, 

 as is well known, has caused enormous losses in years gone by and 

 has invaded our territory on more than one occasion. There is 

 somewhat of a mystery surrounding this insect at the present time 



