60 ANIMAL LIFE AND SOCIAL GROWTH 



sonally visited this region will remember also the 

 presence of the mosquito hordes which breed in 

 the sloughs and infest their neighborhood. 



In the aspen forests where the aspen trees 

 dominate the community and where formerly the 

 American elk, the bison, deer and bear were com- 

 mon animals, today the most influential animal 

 of the community is a mere beetle of the genus 

 Saperda. To the lay mind even a meadow mouse 

 would seem important as compared with one of 

 these beetles. Their importance depends upon 

 their numbers and upon the fact that they feed 

 upon the dominant aspens and in turn are fed 

 upon by woodpeckers. 



The bird population in these woods is much 

 greater than in the open country both in species 

 and in numbers of individuals. The insect popu- 

 lation is decidedly less than in the neighboring 

 communities; the maximum for the year is only 

 4,500,000 and the fall minimum is a mere quarter 

 of a million per acre. Individually most of these 

 insects are of no importance; even as species only a 

 few reach even relatively slight importance in 

 the general community organization, but as a 

 whole they form one of the main sources of food 

 for the bird population and for many small 

 mammals and are of further importance because 

 of the damage they do to plant life. 



