THE ENTOMOLOGIST IN THE FOREST 87
viz. Hybernia defoliaria, H. aurantiaria, H. pro-
gemmaria, and Cheimatobia brumata among the
Geometrae, and Tortrix viridana, one of the
Tortrices. Several other species also assist in the
ravages, but the quintet mentioned are the greatest
enemies to the green-wood.
The life-histories of the four Geometers are
similar. The moths emerge in the autumn or
winter from the pupae, which are subterranean.
The female moths are nearly or quite wingless ;
they can therefore only get at the twigs of the trees
whereon to deposit their eggs by crawling up the
trunks. The males have ample wings, and are to
be readily found at night by the aid of a lantern.
From the eggs laid on the twigs emerge at the
time of bud-opening countless hordes of "looper"
or geometriform caterpillars eager to begin their
attacks on the tender foliage of the forest
trees.
The habits of the pretty Tortrix viridana are
different. Although so destructive to the oaks,
we cannot refrain from admiring it as quite a little
woodland gem, bright apple-green, with pure white
Underwings. The eggs lie dormant during the
winter and hatch out in the spring. The young
caterpillars form habitations for themselves by
twisting up the oak leaves into little cylinders,
inside which they find security and food. When
full-fed the pupa state is assumed within the tube,
and the moth emerges in July.
This little Tortrix and Cheimatobia brumata
are mainly responsible for the defoliation of the
oaks. At the slightest movement of the branches
the Tortrix slips out of its tube, and the Geometers
also quit hold, both hanging down a few feet by a
silken thread until the danger is past, or if dashed
to the ground by a strong breeze they ultimately
remount the tree trunks, never ceasing as they
travel to lay down their silken threads. The
trunks and branches of the oaks thus frequently
get quite overlaid with an unsightly matting of silk,
and the spectacle of the defoliated branches, from
which countless caterpillars sway by silken threads,