20(i THE ENTOMOLOGIST S RECORD. 



production of the colour? I ought to have added that the brown 

 scales and yellow scales are different, the brown have teeth and are 

 more finely striated (in the proportion of 3 to 2) than the yellow ; the 

 latter have no teeth, and therefore would not scatter the light but 

 reflect it more in mass, the stri^ are also more raised, and the white 

 scale has the appearance of being more distended with air. 



I would ask readers to add after the words " black pigment " (mite, 

 p. 85, 17 lines from the bottom) — "in the sense of the other pigments, 

 inasmuch as black is not a distinct colour." — W. S. Riding, M.D. 

 Feb. rsth, 1895. 



The " pigment " question touches ground at last, and curiously 

 enough, just where it was expected not to do so. The fact of a white 

 "pigment" or " white pigment-factor" appears to be proved by the 

 quotation made by Mr. Tutt. I wish I were younger, had better eye-sight 

 and were more leisured, that I might take up the matter in its chemical 

 aspects. Granted that a " pigment " or " pigment-factor " has been 

 detected and isolated in some whites, analogy would seem to suggest 

 that other pigments should be modifications of the same form of matter. 

 It may be so or it may not. Could I attack the subject practically, I 

 should look along that line. But whilst we must admit that some 

 whites are produced by pigment, we cannot deny that other whites 

 are caused by structure, so that we may all be right. I remember 

 many years since reading in the Chemical News, vol. xv. (18B7), p. 299, 

 a note upon the colouring matter or pigment (turacine) which beautifies 

 the Aving and tail feathers of the South African lory (Turacas albocris- 

 tatus). Analysts prove that this colour contains copper. I have shot 

 and eaten many a lory, and always found the whole body — flesh and 

 bone — stained through with the colour, and the crop full of the purple 

 berries of a sort of wild grape. Whether the colour of turacine is due 

 to copper or not I do not know, but — What is the nature of the colour 

 of birds? Prof. Church isolated 1-6 grain of pigment from each bird 

 at a cost of 10s. 6d. ! ! Turacine dissolved in slightly alkaline 

 solutions, and was precipitated (i.e. isolated) by hydrochloric acid. Is 

 not the lovely " gloss " of freshly caught insects a proof that form has 

 a share in tlie decoration ? I take it that the dull disappointing appear- 

 ance of a set and dry insect, is caused by some slight change brought 

 about by drying, the latter being sufficient to destroy some of the 

 diffractive effects of the scales. The " black " question requires more 

 thought. Of course, one can imagine that in some cases the chitin is 

 not so colourless as in others. May be some is stained almost black 

 itself— and also backed by pigment granules, also black. A pure black 

 is, I believe, the most difficult effect to obtain, because it requires the com- 

 plete absorption of all light rays ; and there must l)e different degrees of 

 absorption, i.e. more or less complete. I believe there are vari- 

 ous qualities of lamp-black, as I know there are of black cloth. The most 

 beautifully coloured Papilio that I met with in South Africa— a lovely 

 mother-of-pearl with, I believe, oblique lines of red-brown — has a 

 curious habit of haunting the insides of thorny bushes, where its charms 

 are not only " lost to sight " but are also " to memory dear " if one goes 

 for it with a net. My impression is that it did not seek the light of 

 day where best it could be admired. Why are so many nocturnal 

 insects brightly coloured? Can they admire one another in the 

 dark ? Does not " natural selection " require that such decoration 

 should be seen and appreciated ? — C. R. N. Burrows. March 1st, 1895, 



