51 



THE PROBABLE CHEMICAL AND PHYSICAL NATURE 

 OF THE PIGMENTS OF LEPIDOPTERA.* 



Only a beginning has, as yet, been made in the study of the 

 nature of the pigment substances that are found within the scales 

 of Lepidoptera. Costef and Ureeh | have carried out extensive 

 series of experiments which show that many of the pigment sub- 

 stances may be dissolved out of the scales by means of chemical 

 reagents, giving coloured solutions, and leaving the scales white 

 or colourless. They have also shown that some of these pig- 

 ments may be changed in colour by the action of reagents, and 

 then restored to their original colour by the use of other reagents, 

 For example, many reds are changed to yellow by the action of 

 HCl or HNO3, and may be restored to the original red colour by 

 the use of ammonia. Their researches show that reds, yellows, 

 browns, and blacks are always due to pigments. In a few cases, 

 greens, blues, violets, purples, and Whites are also due to pig- 

 ments, and not, as is usually the case, to structural conditions, 

 such as striae upon the scales, &c. 



It is probable that the most universal pigment colours to be 

 met with in the Lepidoptera are the yellowish buff and brown- 

 drab tints, and this is especially true of the nocturnal forms. 

 The diurnal forms have almost a monopoly of the brilliant reds 

 and yellows and the rich blacks, but it is interesting to note that 

 yellowish buff or brown tints are still very common upon those 

 portions of their wings that are hidden from the light, such as 

 the upper costal edge of the hind wing, which is usually con- 

 cealed from view beneath the overlapping fore wing. Wallace § 

 has called attention to the fact that a yellowish or buff tint is one 

 of the commonest and most widespread colours in Lepidoptera. 



Concerning the chemical nature of the pigment substances 

 within the scales, but little has as yet been made known. 

 Hopkins || finds that the white pigments in the Pieridje are due 



* Excerpt from " The Development of the Wing-Scales and their 

 Pigment in Butterflies and Moths." By Alfred Goldsborough Mayer. 

 (' iSulletin of the Museum of Comparative Zoology at Harvard College,' 

 vol. xxix., No. 5). 1896. 



f " Contributions to the Chemistry of Insect Colours " ' The Entomo- 

 logist,' vol. xxiii. pp. 128-132, 155-167, 181-187, 217-223, 247-252, 283-287, 

 309-814, 338-343, 370-374 (1890), and vol. xxiv. pp. 9-15, &c.). 1890-91. 



I " Beitrage zur Kenntnis der Farbe von Insektenschuppen " (Zeitschr. f. 

 wiss. Zool. Bd. Ivii, Heft 2, pp. 306-384). 1893-94. 



§ ' Darwinism.' 494 pp. London and New York. 1889. 



II " Uric Acid Derivatives functioning as Pigments in Butterflies" (Abstr. 

 of Proc. Chem. Soc. Lond. 1889, p. 117 ; also ' Natiu-e,' vol. xl. p. 335). 1889. 

 —"Pigment in Yellow Butterflies" ('Nature,' vol. xlv. p. 197). 1891.— 

 "The Pigments of the Pieridae " (Proc. Roy. Soc. Lond. vol. Ivii. No. 340, 

 pp. 5, 6). 1894. 



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