GENUS PONTIA. 
Ill 
of P. BrassiccE and Rapes. F. Rapes is avowedly 
a very variable insect, and being too, as well as P. 
Brassicce, a most abundant species, there is conse- 
quently the more scope, — there are so many more 
chances — for variation to take place in the individuals. 
It must be admitted, indeed, that when a Bmall and 
perfectly immaculate specimen of P. Metro is com- 
pared with a full sized and strongly marked one of 
P. Rapie, the prima facie difference is so wide, that 
any one would at once pronounce them distinct. 
But then, on the other hand, we find that interme- 
diate specimens occur, which, presenting every pos- 
sible shade and gradation of difference, appear natu- 
rally to connect and identify the two extremes ; and 
it would be next to impossible to decide, in many 
instances, to which of the two these intermediate 
links should with more propriety be referred. The 
same observations apply also to the kindred species P. 
Napi, the earliest spring specimens of which are 
smaller than those of the summer brood, paler in their 
markings above, and sometimes also entirely destitute 
of them ; and this species too, like P. Brassicce and 
Rap. r, is subject to endless variations. No material 
difference lias yet been observed in the caterpillar or 
chrysalis of the early whites, to distinguish them from 
P. Brassicce and Rapce ; and the distinctions in the 
markings, &c. pointed out by Mr Stephens in proof 
of their being genuine species, seem scarcely sufficient 
to outweigh what may be urged on the other side."* 
* Loudon’s Mag. of Nat. History, iii. 242. 
