THE LARGE GARDEN WHITE BUTTERFLY (Pieris Brassicæ.)
([Plate IV]. fig. 2.)
Why this butterfly should so far outnumber every other native species (excepting, perhaps, the more rural Meadow Brown), is a question beyond our power to answer satisfactorily. Certainly, the food plants of the caterpillar—cabbages, cresses, and their tribe—are universally met with; but then we find there are other insects whose food plant is equally plentiful and widespread, and yet they are nevertheless very rare or local.
This is pre-eminently the domestic butterfly, abounding in suburban gardens, and at times penetrating into the smoky heart of London, and then even the young "St. Giles's bird," whose eyes were never gladdened by green fields, gets up a butterfly hunt, and, cap (or rag) in hand, feels for the nonce all the enthusiasm of the chase in pursuit of the white-winged wanderer, who looks sadly lost and out of place in the flowerless, brick-and-mortar wilderness.
This and the next species are the only British butterflies who can be charged with committing any appreciable amount of damage to human food and property. In the winged state, indeed, it is utterly harmless (like all other butterflies); but not so the hungry caterpillar progeny, as the gardener knows too well when he looks
at his choice cabbage rows all gnawed away into skeletons.
In some seasons and places they multiply so inordinately and prodigiously as to deserve the title of a plague of caterpillars, and several remarkable instances of this phenomenon are on record.
A note in the Zoologist, p. 4547, by the Rev. Arthur Hussey, gives us the following:—"For the last two summers many of the gardens of this village have been infested by caterpillars to such an extent that the cabbages have been utterly destroyed." When the time for changing to the chrysalis state arrived, the surrounding buildings presented a curious appearance, being marked with long lines of the creatures travelling up the walls in search of a suitable place of shelter for undergoing their transformation. A great number of the caterpillars took refuge in a malt-house, from which they could not escape as butterflies, the result being that for several weeks the maltster swept up daily many hundreds of the dead insects.
In 1842, a vast flight of white butterflies came over from the Continent to the coast about Dover, and spreading inland from thence, did an immense amount of damage to the cabbage gardens; but so effectually did the ichneumon flies do their work, that an exceedingly small proportion of the caterpillars, resulting from this flock of immigrants, went into the chrysalis state, nearly all perishing just before the period of change.