LUTESCENT ABERKATION OF EPINEPHELE TITHONUS. 255 



these species become very yellow, and lead insensibly into the 

 normal brown coloration. It would seem therefore that the 

 general action of alkalies, in this direction, is to develop pro- 

 gressive coloration — white (pigmented) to yellow, and yellow to 

 red (-brown) ; whilst Mr. Coverdale wrote ill 1886 (error for 

 1884),* that ' a great many acids (hydrochloric, nitric, sulphuric) 

 restored the pigment, when thus changed to its natural colour.' 

 Whilst dealing with this relation of brown and yellow, I would 

 notice that the dark brown edging to the anterior wings of 

 Epinephele tithonus, Ca'nonympha pamphilm ab. lyllits, and their 

 allies is much more readily acted on than is the orange colour in 

 this species, which is rather remarkable when the colours are 

 considered in their genetic relationship, but is not at all so from 

 a varietal point of view. The unstable character of this band is 

 very marked, and only occurs occasionally in certain varieties of 

 some species, although it is quite constant in others. Here then 

 we notice that a colour in a condition of transition or formation 

 may be, and probably is, more unstable than the colour from 

 which it springs, although the latter, genetically considered, is 

 of course lower than the former. . . . The transitional and un- 

 stable character of the darker colour in Epinephele and its allies 

 gives a decided proof of their probable recent development. The 

 brown found in those varieties of Angerona priinaria, in which 

 the bright orange is reduced to a patch in the central area of the 

 wing, is also of a very unstable nature, and easily affected ; not 

 so the orange, which is particularly stable," &c. 



It is many years since I interested myself in this branch of 

 the subject, my notes, that I published in 1891, having been 

 made between 1881 and 1884, or thereabouts, possibly before I 

 had contributed to any entomological magazine ; but it seems to 

 me that the explanation offered is a sound one with this addi- 

 tion. The recent researches into the structure of the scales of 

 Lepidoptera, and the physiological conditions involved, both 

 subjects which I have recently dealt with at length, suggest that 

 whenever a natural aberration is the result of the degradation of 

 a pigment considered genetically, it sometimes produces much 

 the same result as the reduction of the pigment treated chemi- 

 cally — that is to say, both may produce atavic results ; in fact, 

 these natural aberrations are the only guide one has to tell 

 whether the colours produced chemically are indeed primitive 

 forms of the coloration of the insects or not. At any rate, tbat is 

 the only explanation I have to offer of the fact that these aberra- 

 tions are so generally distributed among orange-coloured species 

 with a tendency for some part of the orange to be replaced by 

 some darker shade of brown. 



I may add that I have a recollection that this particular 



■'• " The Action of Ammonia upon some Lepidopterous Pigments," Entom. 

 xvii. pp. 204-20G.— Ed. 



y2 



