GENUS PONTIA. 1 11 



of P. Brassicce and Rapce. JP. RapcB is avowedly 

 a very variable insect, and being too, as well as P. 

 Brassicw, 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 small and 

 perfectly immaculate specimen of P. Metro, is com- 

 pared with a full sized and strongly marked one of 

 P. Rapce ', 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 

 Rapce, is subject to endless variations. No material 

 difference has 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."* 

 London's Mag. of Nat. History, iii. 242. 



