298 A NATURALIST IN THE GREAT LAKES REGION 



Begin with a single dandelion plant bearing a single blossom 

 cluster in the ^ear — a slander on the enterprising dandelion — ■ 

 that gives rise to a hundred seeds. Let these find lodgment 

 and next year produce plants that each grow a single blossom 

 cluster that produces one hundred seeds, and so on. It will be 

 a matter of less than ten years before there are enough dande- 

 hon plants to cover every foot of land upon the face of the earth. 

 Or consider the coyote that brings into being a litter of eight 

 or nine pups at a time. Suppose these are half male and half 

 female and require two years to reach sufficient maturity to 

 breed. Let the breeding life be only five years, and if nothing 

 interfered with the multiplication of a single pair and that of 

 their offspring inside of half a century there would be a coyote 

 for every square foot of earth. The rancher who has tried to 

 exterminate his coyote neighbors, or the householder who tries 

 to keep his lawn free from dandehons, knows that the possibili- 

 ties are not overdrawn. 



As a result of such astounding fertility, usually more or less 

 held in check by enemies that prey upon the offspring, there is 

 every now and then an overflow of a species from its habitat 

 into the surrounding territory, where if conditions are favorable 

 it permanently establishes itself. The Rocky Mountain locusts 

 have repeatedly appeared in great hordes in the plains states 

 near the mountains, a devastating army that comes in clouds, 

 darkening the sun, that leaves cornfields as barren wastes within 

 a few hours after ahghting upon them, plagues of locusts that 

 have inflicted millions of dollars of damage on crops covering 

 wide areas. The Lapland leming is a small rodent which every 

 ten or fifteen years moves out from its home through surrounding 

 regions in vast numbers, devouring every green thing and usually 

 being devoured by hawks, owls, foxes, and other species of preda- 

 tory animals that follow in its wake in numbers. In the 

 Farmers^ Bulletin No. jj2, United States Department of Agri- 

 culture, is described a plague of mice in the Humboldt Valley, 

 Nevada, from which a few sentences are quoted. 



