A contemporary account states that these were the small white butterflies (_Pieris Rapæ_).
The smaller butterfly with more dusky markings, formerly known as _P. Metra_, has been recently proved to be merely a variety of _Rapæ_, a Mr. J. F. Dawson having reared a brood of caterpillars all _exactly similar_ in appearance, which eventually produced every variety of _P. Rapæ_ and _P. Metra_.
Mr. Curtis, in his "Farm Insects," mentions the capture, near Oldham in Lancashire, of a male specimen, which had all the wings of a _bright yellow_ colour.
Most juvenile butterfly hunters, unblest by scientific knowledge of insect life, imagine that this and the last owe their difference in size simply to their being old and young individuals of the same name; forgetting--or, rather, never having heard--that butterflies never grow in the slightest degree after once getting their winged form; only as caterpillars do they grow. { 86}
The male is distinguished from the female by having only _one round black spot_, or sometimes none, on each _upper_ wing, whilst the female is spotted as in the engraving. The under side of the hind wings is dull yellow, lightly powdered with black scales.
The _butterfly_ is seen during nearly the whole of the summer, and is found almost everywhere.
THE GREEN-VEINED WHITE BUTTERFLY. (_Pieris Napi._)
Is so called from the greenish tint that _often_ borders the veins or nervures on the _under_ side of the _hind_ wing; but the name is _not always_ an appropriate one, for a large proportion of the specimens met with have the veinings grey, and not at all green; but the fact is, that the ground colour varies greatly, from creamy white to full buff, or bright clear yellow; in the latter case it is, that the minute black scales which border the course of the nervures, covering over the yellow, produce a grey-green effect on the eye.
The size also is very variable. I have a specimen that expands two inches and two lines across, from tip to tip, and have seen another not larger than a small Copper butterfly--little more than one inch from tip { 87} to tip. The intensity of the dark markings, on both the upper and under sides, is also subject to much variation.
But, under all these circumstances, the presence of dark cloudy veins on the under side--appearing, but less distinctly, on the upper side--will at once distinguish it from the last species, the only one with which it can possibly be confounded.