6 Presents. [Nov. 15, 



peratnres. The product so obtained was originally described by 

 Hlasiwetz as " mycomelic acid " ; but evidence is brought forward to 

 show that the substance described and analysed by this chemist was 

 in reality urate of ammonium coloured by a. yellow body, probably 

 identical with the natural pigment. 



5. The identity of the natural and artificial products is demon- 

 strated by the fact that both yield under like treatment a purple 

 derivative, which has a well-marked and easily identified absorption 

 spectrum. 



6. The artificial yellow product has not yet been obtained in a pure 

 condition, but it may be so far purified as to exhibit clearly all the 

 general properties of the natural pigment. 



7. The natural pigment as prepared for analysis is shown to be 

 almost certainly a chemical individual. Its probable constitution is 

 discussed. 



8. It is shown that this yellow substance (denominated in the 

 paper " Lepidotic acid "), together with a closely allied red sub- 

 stance, will account for all the chemical pigmentation of the wing 

 scales of the coloured Pierida3, though modifications may be produced 

 by superadded optical effects. The black pigment found in the group 

 is not dealt with in the paper. 



9. The described uric acid derivatives, though universal in the 

 Pieridae, are apparently confined to this group among the Rhopalocera. 

 This fact enables the interesting observation to be made, that where 

 a Pierid mimics an insect belonging to another family, the pigments 

 in the two cases are chemically quite distinct. This is well seen in 

 the genera Leptalis and Mechanitis respectively. 



10. The existence of pigments other than scale-pigments is for the 

 first time described; substances, namely, which are found between 

 the wing membranes, and which, in certain genera, are the basis of 

 ornament. 



11. The fact that the scale- pigments are really the normal excre- 

 tory products of the animal utilised in ornament, is emphasised by the 

 observation that the yellow Pierids, on emergence from the chrysalis, 

 are apt to void from the rectum a quantity of uric acid coloured by a 

 yellow substance which exactly resembles the pigment of the wing" 



Presents, November 15, 1894. 

 Transactions. 



Amsterdam : K. Akademie van Wetenschappen. Verhandel- 

 ingen. Deel II. Nos. 16, 8. Deel III. 8vo. Amsterdam 

 1893-94; Jaarboek. 1893. 8vo. Amsterdam; Yerslagen 

 der Zittingen. 1893-94. 8vo. Amsterdam. The Academy. 



