Lepidoptera The Black-veined White Butterfly – Aporia Cratagi
This butterfly may now be regarded as one of our rarities. At one time it was rather abundant in certain localities in England, among which may be mentioned the neighbourhoods of Cardiff and Stroud, also parts of Kent, Sussex, Hampshire, Huntingdonshire, and the Isle of Thanet; but it is to be feared that this species is nearly or quite extinct in this country. It is well, however, not to give up the search for it, and if you happen to be in one of its favoured localities of former days, you might net all the doubtful ‘Whites’ of large size that arouse your suspicions, liberating them again if, on inspection, they do not answer to the description of the species ‘wanted.’ This course becomes absolutely necessary, since the Black-veined White is hardly to be distinguished from the Common Large White while on the wing.
If you examine a number of British butterflies you will observe that in nearly all species the wings are bordered by a fringe of hair, more or less distinct. But the case is different with Cratagi. Here they are bordered by a black nervure, without any trace of fringe, thus giving an amount of rigidity to the edges (see Plate I, fig. 2).
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 (Cratagus 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 larva, 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 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 pupa may be purchased of English dealers.