174 
HALF HOURS WITH INSECTS. 
[Packard. 
seems to attempt to remove them. The loss of the leaves 
does not kill the trees, but prevents the growth of any 
apples. When these canker worms are fully grown, 7.e., 
about four or five weeks after they are hatched, betweeli the 
17th and 27th of June about Boston, they will be found to 
vary exceedingly in color, some individuals being blackish, 
others greenish-yellow. The average style of coloration is 
an ash color on the back, beneath yellowish, with a black 
stripe on the sides. It has a less number of feet than 
most caterpillars, which gives it a halting, looping gait, as 
if carefully measuring the ground over which it is walking ; 
hence the name geometer. Deserting its tree top it either 
creeps down the trunk of the tree, or lets itself down after 
the manner of most caterpillars by means of a silken thread 
spun from a little opening in its under lip. It doesn’t wan¬ 
der about, but immediately burrows from two to six inches 
in the loose soil under the tree, and then forms a rude loose 
earthen cocoon, fastening the particles of dirt together with 
silk. Twenty-four hours after the cocoon is finished the 
worm changes to a chrysalis, which is rather pointed in front 
and light brown in color. Here the insect remains until 
after the October frosts, when on warm days between the 
cold snaps late in October, and in November and December, 
and even in some exceptionally warm days during the rest 
of the winter, the adult insects come forth. 
Nature has endowed the sexes quite differently ; the male 
is winged and flies about in a modest Quaker garb of gray, 
fluttering with broad weak wings about the trunks of the 
trees and paying court to the grub-like wingless females, 
which are less flighty than their mates. A larger propor¬ 
tion of individuals appear in the spring than winter. This 
provision of nature that a part of the brood shall appear in 
the autumn and a part in the spring ensures the life of the 
species, since if it were not represented in part by the eggs 
and chrysalides, a severe winter might destroy the latter, 
14 
