﻿Chemistry of insect colours. 129 



evident. For although, for my own part, I had always inclined to 

 the view that I now find supported by the experiments presently 

 to be described, yet an entomologist who has devoted so much 

 thought and study to the question as has Mr. Cockerell, arrives 

 at an exactly opposite conclusion to my own concerning the 

 developmental relations of these two colours yellow and white. 

 This at once illustrates the necessity of seeking direct experi- 

 mental evidence as to the correctness of our theories ; and it is 

 not a little astonishing — in view of these considerations — that up 

 to the present this work has been left almost wholly untouched, 

 and a masterly inactivity allowed to prevail in this quarter. So 

 far as I can understand, the chemical behaviour of these colours 

 is veiled in an unlifted cloud of darkness, broken only by the 

 light of some half dozen statements, which are either vague, 

 misleading, or incorrect. For instance, Mr. Wallace * states that 

 the red of Zygcence is changed to yellow by muriatic acid, whilst 

 that of V. atalanta undergoes no such change ; a statement of 

 which the first half is certainly quite correct, but the second half 

 very misleading. Again, there is a general statement that the 

 white of butterflies may be turned yellow by alkalis — a state- 

 ment based on an experiment of Mr. Coverdale's: so far as 

 made concerning Pieris it is utterly erroneous. This has 

 already become known to Mr. Cockerell, who remarks t that 

 " alkali will not turn a Pieris white to yellow." He neverthe- 

 less makes himself responsible for the statement that the white 

 of several species of Lepidoptera may be changed to yellow 

 by alkalis, + a statement that demands careful qualification. 

 And lastly, Mr. Cockerell states that the yellow of a Colias was 

 changed to red by potassic cyanide; a phenomenon so extraordinary, 

 and so utterly opposed to every experimental result yet obtained 

 by me, that I must be pardoned for emphatically discrediting it; 

 at least unless Mr. Cockerell can personally vouch for the fact. 



This then, so far as I am aware, is the extent of our experi- 

 mental knowledge of the subject up to the present, and there is 

 very evidently abundant room for research. At last, too, interest 

 appears to be awakening, and as generally happens in such cases, 

 several workers are moving simultaneously. Both Mr. Cockerell 

 and myself would appear to be (quite independently) interesting 

 ourselves in this subject; and the colours of the Echinoderms, 

 Worms, Ascidians, Crustacea, &c, form the subject of a most 

 elaborate spectroscopic research just recently communicated by 

 Mr. MacMunn to the ' Quarterly Journal of the Microscopic 

 Society ' ; whereas the colours of plants and flowers have long 

 since been investigated by Sorby, Hansen, Bachmann, Pringsheim, 

 Weiss, Church, and various others. 



Now before proceeding further I must disclaim any originality 

 in the first inception of the idea of investigating these insect 



* ' Tropical Nature' t ' Entomologist,' xxii. 126. 'Entomologist,' xxii. 2. 



