).18 THE ENTOMOLOGIST. 



parable, so far, with the behaviour of the soluble yellows and 

 chestnuts ; and it is exceedingly interesting that we should find 

 the same green pigment in such very divergent groups as Noctuse, 

 Geometrse, and Tortrices ; whilst the evidence of the exotic 

 Papilionidse extends this statement to the Bhopalocera. As to 

 the case of Cidaria, I am inclined to think it not impossible 

 (though I am not sure about this point) that the exception may 

 be no more real than is the behaviour of Vanessa io among the 

 chestnuts ; I mean that the green of Cidaria may be identical 

 with that of the remaining species, but developed on a grey or 

 brown ground wing instead of on a white.* If this supposition be 

 correct, these two species are of especial interest. 



Now, any reader who will turn to the original tables of 

 reactions,! published last August, will observe that in the case of 

 Halias prasinana I especially emphasised the somewhat startling 

 phenomenon that one reagent (ammonia) turned the green to a 

 prominent yellow; not a pale, dubious yellow, but a genuine 

 " ochre-yellow." This phenomenon is not, moreover, entirely so 

 isolated as might appear at first sight ; for in the case both of 

 M. orion and D. aprilina a faint yellowish tint was produced by 

 nitric acid. Neither are parallel instances wanting among the 

 Geometrse ; for in both H. strigata and M. margaritaria a 

 yellowish tint was produced, whilst it is noted that N. vernaria, 

 under the influence of acetic acid, changed from green to white, 

 " passing through a phase with pale yellow streak." 



Turn we now for a moment to the Papilionidse. When I first saw 

 the beautiful leaf-green of P. codrus, agamemnon, &c., I concluded 

 it pretty certainly to be a pigment colour. But the earlier expe- 

 riments did not seem to bear out this view : for instance, both 

 these species were unaffected by the acids ; but the other two 

 species noted were more amenable ; and in all cases the greens 

 were acted on by potassic and sodic hydrates. + I concluded, 

 therefore, that the green was identical with that of our English 

 Heterocera, already referred to, although of a somewhat more 

 stable or less soluble character. But there is yet stronger 

 evidence ; for, as shown above, the effect of the alkalis was to 

 change the green of codrus into a yellow, which was permanent 

 when looked at five days afterwards. In the case, too, of 

 policenes, although the wing was not yellowed, yet the solution 

 of the dissolved pigment was ; or, to quote the entry made in my 

 note-book, it " dissolved as yellowish." We may, therefore, very 

 safely consider, I think, that the Papilionidse green is practicall}' 

 the same as that of the other species. 



Now let us revert to the " yellowing " phenomenon : how is 

 this to be interpreted ? The facts, so far as they go, appear to 



* Entom. xxiii. 340. 

 t Entom. xxiii. 252. 



X With this cf. the fact that chestnut seems in many cases more soluble in 

 alkalis than in acids. 



