190 THE ENTOMOLOGIST. 



be correct, we may anticipate the following occasional variations 

 to a former state, — retrogressive varieties, that is, or cases of 

 arrested development : we should find j^ellow varieties of red and 

 pink species ; chestnut varieties of a few red species, such as 

 atalanta, acontia, &c. ; and yellow varieties of green species ; 

 also colourless or very light varieties of yellow and chestnut 

 species, when the pigment, that is, fails to be developed at all; or 

 in a few cases of such non-development of pigment the variety 

 should be black, e. g., in V. io and antiopa, where the chestnut 

 pigment has been developed on a formerly black wing. It is 

 more questionable whether we should be likely to obtain varieties 

 showing such extreme reversion as white for red : after what 

 has been said in a previous section* on the evolution of red, it is 

 clear that such variation would imply reversion to a very ancient 

 state ; still, I should not be surprised at a colourless variety, 

 e.g., Delias, where either the evolution of red has been very rapid, 

 or where anyhow the pigment is by no means so stable as in 

 most red species. t A white variety of green species would less 

 surprise me. 



And secondly, we might get progressive varieties, that is, a 

 normall}'^ colourless species might be found pale yellow or chest- 

 nut, a yellow or chestnut species might be found red, or a yellow 

 might be green ; so, too, an unusually deep variety of the normal 

 colour might appear. All such variation would be in entire con- 

 cord with the theories laid down in these articles as to the evolution 

 of colour; and moreover the abnormal colouring would usually (in 

 all probability) be found as the normal type of an allied species or 

 genus. It is, however, clearly unlikely in a very high degree that 

 we should find a red or green variety of a white species ; the leap 

 would be too great. There is yet another possibility ; if red and 

 green are both descended from yellow, it is, perhaps, conceivable 

 that a pigment normally green should, under abnormal circum- 

 stances, be developed as red — or vice versa — by a diversion from 

 the normal metabolic process after reaching the yellow stage. If, 

 however, any blue variety of a pigment colour should occur — or 

 vice versa — that would be a phenomenon of an entirely different 

 nature, and one which cannot be considered under this category. 

 I will now briefly refer to a few instances that illustrate the 

 foregoing remarks : — 



A. Colourless varieties of chestnut species. There have been 

 noticed in the 'Entomologist' white varieties of G. janira 

 (Entom. xxii. 279),+ milk-white or "silver " varieties of L. phloeas 

 (Entom. xxii. 257 and 279), albino varieties of C. tithonus 

 (Entom. xxii. 287), and a white variety of C. pamphila (Double- 

 day collection). It is superfluous to point out the exact similarity 



* Entom. xxiv. pp. 11 — 13. 



t See Entom. xxiv. 13. 



J These, I presume, are the same as the so-called "sun-bleached" varieties. 



