Another modification with respect to seasonal change is shown by the
Turnip moth (_Agrotis segetum_) and other allied Noctuidae (Owl-moths).
These are insects with brown-coloured wings, flying after dark in June.
The dull greyish larvae feed on many kinds of low-growing plants,
usually hiding in the earth by day and wandering along the surface of
the ground by night, biting off the farmer's ripening corn, or burrowing
into his turnips or potatoes. On account of the burrowing habits of this
insect it can feed throughout the winter, except when a hard frost puts
a temporary stop to its activity. By April it has become fully grown and
pupates in an earthen chamber a few inches below the surface. The Turnip
moth in our countries is partially double-brooded, a minority of the
autumn caterpillars growing more rapidly than their comrades so that
they pupate, and a second brood of moths appear in September. These pair
and lay eggs, the resulting caterpillars going as Barrett suggests
(1896, vol. III. p. 291) 'to reinforce the great army of wintering
larvae.'

Such underground caterpillars, to a great extent protected from cold,
can continue to feed through the winter. With other species we find that
the larva becomes fully grown in autumn, yet lives through the winter
without further change. This is the case with the Codling moth
(_Carpocapsa pomonella_), a well-known orchard pest, which in our
countries is usually single-brooded. The moth is flying in May and lays
her eggs on the shoots or leaves of apple-trees, more rarely on the
fruitlets, into which however the caterpillar always bores by the upper
(calyx) end. Here it feeds, growing with the growth of the fruit,
feeding on the tissue around the cores, ultimately eating its way out
through a lateral hole, and crawling upwards if its apple-habitation has
fallen, downwards if it still remains on the bough, to shelter under a
loose piece of bark where it spins its cocoon about midsummer and