84 THE entomologist's recokd. 



a totally different colour apjjears, and the same colour (brown) appears 

 if the superficial layer of scales be removed. When the insect is dried 

 again, the gi'een colour returns. 



With regard to the metallic spots in lepidopterous (Vanessid) pupa3, 

 the appeai-ance is due to alternate layers of water and chitin, and, 

 according (I believe) to Poulton, these are arranged in cubical cells. 

 This arrangement was discovered by a German observer whose name 

 I now forget. 



With regard to black colours, I quite agree with Mr. Tutt, that there 

 are two kinds of black. My idea is, that one is a black that is always 

 associated with a pattern, as in the Pieridae, Papiltos and other butter- 

 flies ; the other black being a more or less diffused black not associated 

 with a pattern, which, if increased, gives a melanic insect. Limenitis 

 sibylla has a black form, produced by the extension of the black colour, 

 but this is not what I call melanic, and I am beginning to doubt 

 whether the time-honoured var. doubledayaria, of Amphidasys hdidaria, 

 is not also an extension form, and, although the extension may serve 

 the same purpose, it is not the result of the same process as that of true 

 melanism, which arises from suffusion. 



I find that I have not answered Mr. Tutt's question about pigment 

 granules. I have always considered that the pigment granules do not 

 contribute to any great extent to the colour of the insect, for, as far as 

 I could make out, the colour seemed to be dispersed throughout the 

 scale and not confined to the pigment granules, and I think it jjossible 

 that these granules have no special colouring function, although they 

 may be impregnated with, or perhaps only surrounded by the scale 

 colour. I am convinced that these granules are present in very much 

 greater abundance in melanic, and what I may call quasi-melanic 

 specimens, i.e., those small brightly-coloured specimens one gets occa- 

 sionally when breeding insects. Perhaps it would be more correct to 

 call them more deeply coloured. I have some specimens of PanoNs 

 piniperda which show this very well. Possibly these granules may be 

 expressions of waste energy only, and have nothing to do with the 

 colour. With regard to what I wrote in my last note about the different 

 refractive indices and " the shining through of the under scales," I will 

 try and put it more clearly. In the case of T. rnbi, when the scales are 

 drj', the superficial layer of scales being of a different refractive index 

 from the brown scales beneath, a green api^earance is produced. When 

 wetted, the refractive index is changed, or more probably its power of 

 refraction is lost, then it becomes a mere transjjarencj' through which 

 the brown shows. I do not know of any pigment whose colour is 

 altered by being wetted. I think I have written enough on pigment 

 this round, and will wait and see what my betters have to say. — 

 E. Fkeek. M.B., Eugeley, Staffs. Dec. I8th, 1894. 



In my notes on pigment {Ent. Record, vol. vi.. No. 2, p. 38, line 9), 

 " diffraction of thin films " should read " diffraction or thin films." In 

 the next line, I fear my meaning is oi^en to misinterpretation. I ought 

 to have Avritten " all the brilliant iridescent colours of insects .... are 

 due to interference &c.," instead of " all the metallic colours and their 

 iridescence .... are due," &c. What we call metallic blotches, as we 

 know them in the genus Pliisia, Sic, seem to be caused both by the pig- 

 ment and the scale structure. A large amount of white light is reflected 

 in mass from the surface (as in metals), and this carries with it some 



