52 THE ENTOMOLOGIST. 



to uric acid, and also that the red and yellow pigments are due 

 to two closely related derivatives of uric acid. These uric 

 acid derivatives used in ornamentation are apparently confined 

 to the Pieridai among l)utterflies. For when a pierid mimics 

 an insect of another family, the pigments in the two cases are 

 chemically quite distinct. This is well seen in the genera 

 Leptalis (Pieridte) and Mechanitis (Danaidte). 



Further, Griffiths * lias shown that the green pigment found 

 in several species of Papilio, Ilesperia, and Limeitiiis among 

 butterflies, and of NoctuidaB, Geometridre, and Sphiugidfe among 

 moths, also consists of a derivative of uric acid, to which he 

 gives the name " lepidopteric " acid, and assigns the empirical 

 formula CnHioAz NyOio. By prolonged boiling in HCl it is con- 

 verted into uric acid. 



Urech t demonstrated that in a large number of Lepidoptera 

 the colour of the urine that is voided upon emergence from the 

 chrysalis is similar to the principal colour of the scales. 



Landois I many years ago made a careful study of the con- 

 stitution of the blood of several species of beetles and butter- 

 flies. He found that when the blood is allowed to evaporate in 

 the air, crystals separate out. He also found that the blood 

 consists chiefly of egg albumen, but that globulin, fibrin, and 

 iron are also present. He called attention to the fact that the 

 freshly drawn blood of the larvae of Lepidoptera is usually light 

 in colour, but that when it is allowed to dry in the air it 

 generally becomes brownish or yellowish ; and further, that 

 while the colours of the bloods are difterent for different species, 

 it is very remarkable that the colour which is assumed by the 

 dried blood is apt to be similar to the ground colour of the wings 

 of the mature insect from which the blood is drawn. 



As before stated, I believe that the pigments of the scales 

 are derived from the ha?molymph or blood of the chrysalis, and my 

 chief reason for believing this is that I can find no evidence that 

 there is anything but hnemolymph within the scales during the 

 time when the pigment is formed. In considering the pheno- 

 mena of pigmentation, therefore, it is important to know as 

 much as possible about the pbysical and chemical properties of 

 the haemolymph of the pupa. Accordingly, I have devoted some 

 time to the study of the properties of the pupal htemolymph of 

 the large Saturnida?, Samia cecropia, Callusamia promcthea, and 

 Philosamia cyntliia. The haemolymph is under considerable 



"' " Eecherches sur les Couleurs de quelqiies Insectes " (' Coiuptes Reudus,' 

 Acad. Sci. Paris, tome cxv. pp. 958, 959). 1892. 



f " Beobachtungeu iiber die verschiedenen Scluippenfarben iind die zeit- 

 liche Succession ihres Auftretens " (Zoolog. Anzeiger, Bd. xiv. pp. 46G-473). 

 1891. 



I "Beobachtungeu iiber das Blut der Insecten " (Zeitschr. f. wiss. Zool. 

 Bd. xiv. pp. 55-70, Taf. vii.-ix.). 1864. 



