The wing rays, or nervures, are very distinct—a feature that
gave rise to the popular name of the butterfly. In the male they are quite or nearly black, but those of the fore wings of the female are decidedly brown in colour. At the terminations of the wing rays there are triangular patches of dark scales, the bases of which unite on the outer margins of the wings.
Another peculiar feature of this insect is the scanty distribution of scales on the wings. This is particularly so in the case of the female, whose wings are semi-transparent in consequence.
The butterfly is on the wing during June and July, at which time its eggs are laid on the hawthorn (Cratægus Oxyacantha) or on fruit trees—apple, pear and plum.
A vigorous search of these trees in the proper localities may reveal to you a nest of the gregarious larvæ, all resting under the cover of a common web of silk. These remain thus under their silken tent throughout the hottest hours of the day, and venture out to feed only during the early morning and in the evening.
When the leaves begin to fall in the autumn, they construct a more substantial web to protect themselves from the dangers of the winter, and in this they hybernate till the buds burst in the following spring. They now venture out, at first during the mildest days only, and feed voraciously on the young leaves, returning to their homes to rest. Soon, however, they gradually lose their social tendencies, till at last, when about half or three-quarters fed, they become quite solitary in their habits.
In May they are fully grown, and change to the chrysalis state on the twigs of their food trees.
The larva is black above, with two reddish stripes. The sides and under surface are grey, the former being relieved by black spiracles.
The pupa ([page 45]) is greenish or yellowish white, striped with bright yellow, and spotted with black.
It is probable that the reader will never meet with this insect in any of its stages. But, though it may have left us, it is still very abundant on the Continent, where it does great damage to fruit trees; and the foreign pupæ may be purchased of English dealers.