﻿CHEMISTRY OF INSECT COLOURS. 343 



still be raised, viz., that, granting the above, yet the yellow pig- 

 ment, as soon as produced, ought to be dissolved by the reagents 

 employed, leaving the wing finally colourless, as in Euchloe or 

 Colias, for example. To which I reply that, in the first instance, 

 not all yellows are dissolved ; and, in the second, that on repeating 

 my experiments with special reference to this point, I find that in 

 every case the reagent which produces the colour also dissolves 

 it (a fact observed from the first as true of some reagents), leaving 

 a colourless transparent wing. So that we may fairly consider 

 galatea to offer no contravention to the general rule. 



The next species to which I will call attention is Amphidasys 

 betularia. Knowing that buff- coloured varieties of this species 

 occur, I was exceedingly interested to learn how reagents would 

 affect this white. Most of them were absolutely without effect 

 (as usual), but after treatment with sulphuric acid there were one 

 or two very small but distinct buff spots or marks on the wing. 

 The same effect was produced by potassic permanganate, and 

 somewhat doubtfully by tannin and by gallic acid. This was 

 rather exciting ; and, in the hope of transforming the white 

 entirely, I specially experimented by submitting wings of this 

 species to the action of sulphuric acid for an entire week. To 

 my great disappointment, however, at the expiration of that 

 period, the white was really not affected at all, except that the 

 veins were buff. Had the experiment succeeded we should have 

 had a companion case to that of galatea; but as it is I am some- 

 what a loss to understand why such a very trifling effect was 

 produced, and nothing more. It is, however, very possible that 

 this species is in an analogous condition to galatea, but that the 

 " mother-substance " of a pigment is in most specimens less far 

 advanced in the metabolic progress. I should dearly like to test 

 (if there be such) a white specimen bred from one normal and one 

 buff parent, — since one might expect that in this instance a 

 pigment could be readily produced by the same method as in 

 galatea. If so, one might next experiment on a " quadroon " 

 specimen, and so on. 



Of the remaining species there is very little to be said. The 

 peculiar behaviour of Hepialus humuli may be pointed out. I 

 cannot understand why this white, which presents such a fine, 

 almost polished, appearance, should " go transparent " under the 

 action of most reagents. But this is a puzzling and unsatisfactory 

 species altogether. The natural quasi-transparency of the white 

 in Vanessa, Limenitis, and many Noctuae and Geometrse, was even 

 more evident under the influence of various reagents ; and with 

 this may, perhaps, be correlated the fact that they stained so very 

 slightly (see p. 220). 



With this, I think, concludes all that need at present be said 

 about while, and we may now pass to the consideration of some 

 pigment colours. 



(To be continued.) 



