INTRODUCTION. V 
is done to the tree by these voracious beings. The process up to a 
certain limit may be one of natural and healthy pruning, but there is 
no certainty that the limit may not at auy time be overstepped and 
destruction ensue. The tree is attacked in a multitude of ways by cater- 
pillars alone. The buds are eaten by various leaf-rollers (Tortrices), 
the leaves are mined on the upper and under sides by various Tineids, 
while the leaves are rolled over in various ways and in various degrees 
to make shelter for the caterpillars, or they are folded ou the edges, or 
gathered and sewed together by Tineid, Tortricid, and Pyralid larvae. 
The entire leaves are devoured by multitudes of species of larger cater- 
pillars, belonging especially to the Pyralid, Geometrid, Bombycid, and 
Sphingid moths ; while certain species prey on the fruit, acorns, nuts, 
and seeds. 
It is a singular fact that of the great family of Owlet or Noctuid 
moths, of which there are known to be 1,200 species in this country, 
very few feed on trees, the bulk of them occurring on herbaceous plants 
and grasses. 
While the smaller caterpillars (Microlepidoptera) feed concealed 
between the leaves or in the rolls or folds in the leaf, or in the buds, the 
caterpillars of the larger species feed exposed on or among the leaves. 
Here they are subject to the attacks of birds aud of Ichneumon and 
Tachina flies, which are constantly on the watch for them. And it is 
curious to see how nature has protected the caterpillars from observa- 
tion. While the young of the smaller moths are usually green and of 
the same hue as the leaves among which they hide, or reddish and 
brownish if in spruce and fir buds, where they hide at the base of the 
needles next to the reddish or brownish shoots, the larger kinds are 
variously colored and assimilated to those of the leaves and twigs 
among which they feed. Were it not for this they would be snapped 
up by birds. Of course, the birds devour a good many, and the pry- 
ing Ichneumons and Tachinae lay their eggs in a large proportion, but 
those which do survive owe their safety to their protective coloration. 
Of some twenty or more different species of Geometrid caterpillars' 
which occur on the evergreen trees, some are green and so striped with 
white that when at rest stretched along a pine needle, they could with 
difficulty be detected; others resemble in various ways (being brown 
and warted) the small twigs of these trees ; and one is like a dead red leaf 
of the fir or hemlock. There are several span-worms on the oak, which 
in color and markings, as well as in the tubercles and warts on the body, 
resemble the lighter or darker, larger or smaller knotty twigs; this 
resemblance, of course, is in keeping with the characteristic habit of 
these worms of holding themselves out stiff and motionless when not 
feeding. 
In an entirely different way the various kinds of Notodontian cater- 
pillars, which feed exposed on oak leaves, are protected from observa- 
tion. They feed on the edges of the leaves, and their bodies are green ? 
