8 ANIMAL COMPETITORS 
Hessian soldiers,—a queer echo of the London 
idea that it came there with the Hanoverian 
train of the present reigning house. By 1830 
it had reached the Mississippi, and by 1857, 
at least, was numerous in California.’’ Now 
no part of the country save the western deserts 
is free from these pests; and competent judges 
estimate their numbers as at least five times 
that of the human population, with which they 
more than keep pace as widening civilization 
more and more favors their support and in- 
crease. 
Fecundity of the rat. A consequence is that 
from time to time there is an overflow of rats 
from one locality or region to another which 
gives us a glimpse of the unseen crowd in the 
midst of which we live. ‘‘In 1903, a multi- 
tude of migrating rats spread over several 
counties of western Illinois. They were no- 
ticed especially in Mercer and Rock Island 
counties. For several years prior to this in- 
vasion no abnormal numbers were seen, and 
their coming was remarkably sudden. An eye- 
witness to the phenomenon informed the writer 
