8 THE GENERA AND SPECIES OF BRITISH BUTTERFLIES. 
The chief of these have been formerly described as distinct species by the names of Pontia Metra 
(distinguished by its smaller size), Papilio alba media immaculata (the male of P. Rape), Papilio 
alba media trimaculata (the female of P. Rape), and several others. 
Pievis Napi (the Green-veined Cabbage-White, Nos. 6 to 10) has also been confused both 
with P. Brassice and the species last described, by those unacquainted with entomology ; it is 
however very distinct from both. From P. Lape by the almost constant absence of the black 
spot in the centre of the fore wings of the male, and from both by the peculiar green markings 
of the under side of the hind wings, from which it takes its popular name, the Green-veined 
White. The male (No. 6) is not only without the black spot above alluded to, but also nearly 
without the dark marks at the tips of the fore wings, though they are sometimes much more 
conspicuous than in the specimen represented. The female (No. 7) has the spots, and the marks 
at the tips of the fore wings similar to those of the female of P. Rape, but generally much 
paler. The Caterpillar is distinguished from that of the preceding species by the absence of 
the yellow line down the back. It feeds upon Brassica napus, from which it takes its name, 
and also upon several other cruciferous plants, especially the common cabbage ; in feeding 
upon which, both this and the preceding species do not confine themselves to the external 
leaves of the plant, like the larvee of P. Brassicw, but eat into the heart; they are conse- 
quently much more destructive, and are known in France as the ver du ceur. The Cater- 
pillars appear in spring and autumn, like those of P. Rape. Both the small species of Pieris 
are further distinguished from the large one by the disposition of the eggs, which are laid 
singly, instead of in agglutinated patches. 
The varieties of P. Napi are numerous, among the most remarkable of which are those 
specimens which have the veins of the upper side of the wings rather strongly marked with 
dusky black, which were made a species by H. Srepiens, under the name of P. Sabellice ; and 
the P. Napew, made a separate species by Esper, which is of a larger size than the ordinary 
(pi. 
specimens of P. Ni 
