DEVELOPMENT OF WING-SCALES. 53 



piessure in the chrysalis, and when an incision is made near the 

 shoulders of the wing cases it spurts out in large drops. I have 

 made a chemical analysis of it, and find that its chief con- 

 stituent is egg albumen, but that globulin and fibrin are also 

 present. When the hsmolymph is agitated with ether, the 

 proteid substances are coagulated, and a clear amber-yellow 

 solution is left. This amber-yellow solution may then be 

 decanted off from the congealed proteids. When thus isolated 

 the proteids are slightly yellowish, but they soon dry iuto a drab- 

 coloured mass, very much as the hfemolymph itself does upon 

 exposure to the air. Spectrum analysis shows that the clear 

 amber-yellow solution owes its yellow colour to xanthophyll. It 

 will be remembered that Poulton* found that the green and 

 yellow colours of many lepidopterous larvae and pupte were due 

 to chlorophyll and xanthophyll derived from the leaves of their 

 food-plants. The hoemolymph is acid to litmus, and I find that 

 it actually contains a large amount of orthophosphoric acid 

 (ammonium molybdate test). Mr. George Oenslager has kindly 

 determined the mineral bases of the h^molymph for me, and 

 finds them to be iron, potassium, and sodium. The iron is 

 present in considerable quantity. 



Although the freshly obtained hpemolymph is a clear opales- 

 cent amber-yellow fluid, it soon becomes turbid upon exposure to 

 the air, and in less than half an hour after removal from the 

 chrysalis becomes opaque, and drab or greenish drab in colour. 

 It is interesting to note that the drab colour assumed by the 

 dried haemolymph from the pupa of C. i)romethea is very 

 similar to the drab of the outer edges of the mature wings. In 

 the case of P. cijnthia, also, the hnemolymph dries into a 

 greenish drab colour, which is strikingly similar to the principal 

 colour of the moth's wings. In the case of S. cccropia, however, 

 the hfemolymph becomes rather greener in colour than the drab 

 of the mature wings. 



This curious change in colour which the hsemolymph exhibits 

 upon exposure to the air is probably not a simple process of 

 oxidation, for it will take place in an atmosphere of hydrogen, 

 although rather more slowly than in the air. An atmosphere 

 of CO2, however, practically prevents it, for after remaining for 

 forty-eight hours in this gas, the htemolymph shows only faint 

 traces of a drab-coloured clot around the edges of the liquid, 

 whicli remains clear and amber-yellow in colour. If the hsemo- 

 lymph be sealed up air-tight in glass tubes it will retain its clear 

 amber-yellow colour indefinitely. When the newly extracted 

 clear amber-coloured htemolymph is heated to 5-1^ C, it begins 

 to congeal, and at temperatures above 63" C, it rapidly solidifies 

 into a chrome-yellow-coloured mass. In this condition it will 



■■■■ " The Essential Nature of the Colouring of Phytophagous Larvae and 

 their Pupae, &c." (Proc, Roy. Soc. Lond. vol. xxxviii. pp. 269-315). 1884-85. 



