Not fewer than one hundred and sixty-six different kinds of butterflies are referred to this genus. "They are diffused," says Dr. Boisduval, "nearly over the whole globe, but are particularly abundant in the intertropical countries of the old continent. Considering the extent of the New World, it produces comparatively few species. The most remarkable inhabit Africa, the Indian continent and Archipelago, and New Holland. Such of the caterpillars as are known, feed almost exclusively on the cruciferæ, residaceæ, tropioliæ, and caparideæ. Our P. Cratægi is the only one in Europe which lives on trees; but it is probable that many exotic kinds are of the same habits. The prevailing colour among these lepidoptera is white, more or less pure, with a black border, variable in width, but seldom wanting. There are likewise species in which the ground colour is yellow or even orange, while in others it is blackish or blue, &c. The inferior face of the posterior wings generally differs considerably from the upper, and is often very agreeably varied with brilliant colours. The sexual differences, in certain species, are very conspicuous, particularly on the surface; in others, they are much less so, the females being distinguished from the males only by a somewhat wider border, or by having the upper wings more rounded at the apex[1]."
- ↑ Species général des Lepidoptères, i. p. 435.
