420 Canadian Record of Science. 
others. Nature, protesting against this, multiplies the 
insects that feed upon it, and when these in their turn 
become too numerous, the parasitic species come. We can- 
not however always afford to wait until these get the mas- 
tery, as their work though sure, is often slow, and so we 
have to battle with the bugs for our potatoes, and with 
paris green murder both friend and foe. 
In a circular on the protection of North American birds, 
issued by the American Ornithologists’ Union, the following 
statement is made: “With the decrease of birds at any 
point, is noted an increase of insects, especially of kinds 
injurious to agriculture. The relation of birds to agriculture 
has been studied as yet but imperfectly, but results could 
be cited which go far to substantiate the above statement of 
their general utility.” 
I have seen similar statements in other publications, and 
also, some to the effect that when the birds were again allowed 
to increase, the insects decreased in a corresponding degree. 
These views may be perfectly correct, and are certainly 
very generally held. I have, however, so far failed to find 
anything showing that they are the result of careful investi- 
gation, and it is worthy of notice in this connection, that 
many kinds of insects do at times suddenly increase to an 
enormous extent, and just as quickly die off again, apart 
altogether from any unusual increase or decrease in the 
numbers of the birds. In 1884, the clover fields in the 
Ottawa district were seriously injured by a caterpillar 
which suddenly appeared in immense numbers, it proved to 
be the larvee of Agrotis fenica, a moth which had previously 
been quite a rarity, and probably unknown, except to ento- 
mologists. When almost full-grown they were attackel by 
a fungoid disease which quickly destroyed them, but very 
few producing the moth, nor have they since occurred in 
such unusual numbers. 
In 1881, the pasture fields of Northern New York were 
attaeked by an immense array of caterpillars, entire fields 
being laid waste in ten or twelve days, and in some places 
they were so numerous that they could have been scooped 
