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whose pupae normally resemble polished gold or silver, and obtained pupae 

 having dark brown streaks and spots on this metallic lustre. These, therefore, 

 agreed with the normal pupae of E. LEUCOsricxos Gm. from Java. How is 

 this to be accounted for? It can hardly be attributed to colour. evolution since 

 this metallic lustre is undoubtedly of a structural nature whereas colour evolution 

 in only known in pigmental colours. 



The pupae of some species of Danais also exhibit special phenomena. I 

 have frequently bred those of Danais Chrysippus L. and of D. Genutia Cram. 

 Of the former I obtained many pupae the majority of which were of milky 

 white, some retaining this colour while others subsequently became rose or 

 green. On the other hand I observed that of these pupae, reared in a clear 

 glass cylinder, which were of a beautiful green a portion subsequently turned 

 to a milky white while others under the same conditions remained green. The 

 bred pupae of D. Genutia Cram, were all green at first; some remained of that 

 colour but others subsequently became pale rose. None of these pupae contained 

 parasites. Whether they were reared in dark boxes or in clear glass cylinders 

 made no difference ; one beautiful green chrysalis of Danais Juventa Cram., 

 formed in a very dark box, agreed completely in colour with one found by me 

 in a natural state. In all these pupae golden spots occur which appear as white 

 immediately after pupation and in which the metallic lustre only becomes 

 apparent later. How can these colour differences be explained? I believe in 

 order to arrive at this attention must be paid in the first place to what is 

 known concerning the colour phenomena occurring in the pupae of other 

 butterflies and that, therefore, I must take into account all investigations on the 

 subject, although these mostly have reference not to Danaidae, but to other Lepi- 

 doptera — Papilionidae, Pieridae, and even Heterocera. When some time back 

 I discussed the rearing by Mr. Edw. Jacobson of imagines of Papilio Memnon L. 

 I had also to concern myself with this question. My views in this connection have 

 since been published in the Tijdschrift voor Entomologie liii, igio. I will 

 briefly repeat them here. According to Mr. Jacobson the pupae — about 400 in 

 number reared by him at Batavia on its food plant had, almost without exception, 

 assumed the colour of their immediate environment, those attached to the 

 variegated greyish-brown branches of the citrus tree, on which the larva had 

 been reared, were of the colour of bark with green spots while those fastened 

 to leaves or green twigs were green. A few only had pupated against the 

 white gauze surrounding the larvae on the citrus branches and these were of 

 a dirty white without green spots. Mr. Jacobson expresses the opinion that 

 these results in general agree wMth those obtained by Prof. Dr. J. Vosseler 

 in breeding Papilio Demoleus L. in East Africa but do not correspond with 



