the Charlonia group of the genus Anthocharis. 533 



western headquarters of the yellow form, these two 

 distinct species, the white Pechi and the yellow Charlonia, 

 should obtain. The former, however, is very rare, 

 whilst the latter is common : this shows that the one 

 has not the power of assimilation; consequently selection 

 comes in, keeping the two species distinct, but working 

 to the detriment of the one and to the advantage of 

 the other, so that probably the one is on its way to 

 extinction. 



The latest record of Charlonia from the Canary 

 Islands is very interesting, but perhaps not surprising. 

 The two specimens sent to the National Collection differ 

 in no way from those taken in Algeria. It is most 

 probable that when Marocco is more explored this 

 species will be found all down the north-west coast of 

 Africa, whence it is easily understood how it found its 

 way across the very narrow strip of intervening ocean. 



We may, I think, safely conclude that the present 

 distribution of this little desert group of Anthocharis 

 has been brought about in the manner here suggested. 



PS. — Since writing the above I have received vol. v. 

 of Komanoff's Memoirs, in which Christoph says that a 

 larger number of Tomyris have been received, and that 

 the males are more strongly tinged with yellow than the 

 one figured in vol. i. This supports my view that 

 Tomyris may be gradually assimilating its colour to that 

 of the Cliarlonia subsection of this subgroup. Christoph 

 further says that Staudinger considers that PecJd is 

 probably a Mauritanian variety of Tomyris. With this, 

 however, I cannot agree, as the wings are very different 

 in shape, Tomyris having the apex decidedly rounder 

 and wing broader proportionately. Furthermore, the 

 general appearance of the two insects is quite dissimilar, 

 as may be gathered from the foregoing descriptions. 



