184 
HALF HOURS WITH INSECTS. [Packard. 
apple years. Seasons when through favoring causes certain 
species appear in extraordinary numbers. The causes would 
not seem to be wholly climatic, for during seasons that may 
seem to be peculiarly favorable to insect life, every species 
does not abound in equal numbers. It seems more probable 
that the increase in a species is owing to a decrease in the 
numbers of the ichneumons attacking it, though the causes 
leading to the partial extinction of the ichneumon may be 
unknown. How full of interest would be a study of such 
phenomena as the periodical or unusual abundance of certain 
animals ! No subject could be more attractive to the biolo¬ 
gist, while none is of more practical importance to the gar¬ 
dener or farmer; and it is just such studies as these that 
our young students should take up. 
“In the year 1791,” says Fitch, “the orchards and forests 
of New England were overrun by this worm, and the leaves 
of the apple, oak and other trees were devoured by it. It 
was at this time that it received the name ‘ Palmer worm/ 
by which it has since been currently designated. This name 
was evidently derived from our English translation of the 
sacred scriptures. Another insect, which a month or two 
before had devastated the fruit trees to an extent never pre¬ 
viously known, appears simultaneously to have received the 
name which it still retains, the canker worm ; for previously 
to this date we find this name given to what is now called 
the army w'orm.” (Leucania unipunctata.) “Another re¬ 
markable visitation of these insects occurred in the year 
1853, unparalleled by any event of this kind within the mem¬ 
ory of the present generation.” It appeared “suddenly in 
excessive numbers” from Maine to eastern New York. The 
Palmer worm appears about the middle of June, about the 
time the canker worm is entering the earth, and continues 
till the close of the month. It strips off the foliage, thus 
emulating the gastronomical feats of the canker worm. Dr. 
Fitch says that should, “ after a visitation from these w r orms, 
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