Packard.] 
INSECTS OE THE FOREST. 
245 
change to pupae in the autumn, while others wait till the fol¬ 
lowing spring. The beetle appears in June. 
Now in the remarkable habits of these insects, we find a 
variation in their mode of working corresponding to some 
difference in the size and nature of the branch in which they 
live. This is something quite different from the blind, unva¬ 
rying instinct usually ascribed by the unthinking to the 
lower animals. The oak pruner selects a fitting place in 
which to lay its eggs, and because it does so for generation 
after generation, no one can deny that there was not a time 
when this habit was in process of formation, and gradually 
established after a course of experiments continued through, 
perhaps, many generations. Again, the borer itself is not 
entirely the creature of circumstances; there is some room 
left for the exercise of what we may call judgment. The 
incision it makes in the branch varies in depth with the size 
of the branch, and it must exercise a certain, be it a mini¬ 
mum, amount of reason to adjust its life with the physical 
forces about it, in order that the life of the species may 
be maintained. Doubtless it makes many mistakes, many 
branches falling too soon or not falling at all; many deaths 
occurring from these mistakes. Unfavorable seasons, calm 
weather, a too dry or too moist atmosphere, its parasites, 
all conspire to reduce its numbers and render its struggle 
for bare existence exceedingly precarious. But this is the 
history of every species of animal. The life of each species 
is a record of mistakes, and disease and often death in con¬ 
sequence of those mistakes. And turning to the human 
species, the philosophic historian of his race is forced to 
confess that it is often by their misfortunes that races as well 
as individiKils of marked individualism have moulded their 
characters. We submit, then, that these unusual instinctive 
acts of the oak pruner have been in all probability gradually 
acquired, after many trials, mistakes and failures, until the 
peculiar habits distinguishing this species from its allies 
21 
