56 
JOUENAL OF MAMMALOGY 
It is possible that the vast multiplication of nesting places may have 
resulted in an insupportable increase of parasites in the shelters so that 
the nests had become untenable. But of this there are only two shreds 
of evidence at hand. One^ the known fact^ that overcrowded squirrel 
nests breed abundant parasites; second the squirrels are comparatively 
scarce after the army has gone. Thus the evidence is far from conclusive. 
We have, then, the last cause to consider — over-population. The army 
has always come from a land of plenty — a place of ideal squirrel con- 
ditions— at a time when they seemed at their best, and further, the 
time of migration is always just as the broods of the year are full grown. 
No one has ever recorded a squirrel migrating from a land when they 
were few or moderate in numbers, always from a place where they over- 
abounded. No one has witnessed one of these treks since the squirrels 
became comparatively scarce. 
This explanation is paralleled by the known causes that send the 
Scandinavian lemming and the African springbok millions, out of their 
country and on, till they meet their end; and last, probably most 
exactly, hy the swarming of bees; the sallying forth of the new brood to 
seek a new home, for there is not room in their birthplace. In a word 
then, the graysquirrel swarms as the bees swarm; this explains their 
marching armies. But the dwindling of their numbers has put an end 
to their emigrations. I have not yet heard of one since 1866. 
NUMBERS 
How are we to form any idea of their numbers in primitive time® 
when the whole land was one big harvest field of nuts for their chief 
benefit? 
The early naturalists seemed satisfied to describe the squirrel hordes 
as “astounding,’’ “immense,” “myriads,” “incredible,” or “unbeliev- 
able,” and we rejoice that Kennicott and others of more exact mind 
were born in time to make a more satisfactory record. Kalm relates 
(Travels, p. 320) that in the year 1747 the State of Pennsylvania paid 
bounties for the killing of 640,000 squirrels. In “The Hunter’s Feast,” 
published about 1840 (p. 163) is an account of an all-week Kentucky 
squirrel hunt in which the sides with 6 guns on each, killed respectively 
5000 and 4780 squirrels. 
Robert Monro writes in 1804 of squirrel hunts in western New York 
in which upwards of 2000 squirrels have sometimes been killed in one 
day. (Merriam, Mam. Adirondacks, p. 229.) 
