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followed by the genus Danais ; this therefore, points to a transition phenomenon 

 as regards colour evolution the same as occurs with respect to wing form in 

 the fore-mentioned Dismorphias in South America, in which the one sex is 

 already under the influence, directed in a definite course, but the susceptibility 

 to it has not yet developed in the other, which, consequently, retains the ancient 

 form of wing unchanged. This case is analogous to that of Euploea Midamus L. 

 whose d" is a typical Euploea whereas the 9 principally exhibits the colour 

 adjustment obtaining in the genus Danais and, therefore, resembles D. Agleoides 

 Felder more than a Ei-ploea, pointing also to a state of transition on which 

 hypothesis the Euploea course must have been developed from the one peculiar 

 to the genus Danais sothat the 9 of E. Midamus L. and Elymnias Undularis 

 Drury have retained the old form which, according to the ontogenesis of the 

 Euploea larvae, appears, in fact, to have been the case. 



The same occurs with the other course of colour evolution which, besides 

 the one alluded to, has been followed by the Malayo-Australian Danaids and 

 is most observable in the genus Danais. In addition to the genera Hestia 

 and Ideopsis it occurs also in the different species of Papilio living in the same 

 districts, such as P. Macareus Godt., P. Idaeoides Hew. and others; like- 

 wise in Nymphalidae in species of the genus Hestina Westw. and in Satyridae 

 in species of the genus Zethera Felder and even in the family Zygaenidae 

 already alluded to, inter alia in Isbarta Aspasia Sn. and Cyclosia Papilionaris 

 Drury. Such cases of uniformity in the process of colour evolution or so-called 

 homochromatism are, moreover, known in different genera and families in 

 South America. Bates has referred to it and Blanford discussed it in A'ature 

 of June 2o'ii 1895 ^n<^ indicated several very important instances of it at a 

 meeting of the Entomological Society of Londoti on May s'*" 1897. Its cause, 

 however, was unknown to them. 



When we observe how the appearance of white, which in Euploeas we 

 know to be an expression of the course of the process of colour evolution, 

 manifests itself in the island of Celebes in two species of Euploea occurring 

 there, but likewise in other Malayan islands, E. Viola Bud. and E. Schlegelii 

 Voll. in a different manner from what obtains in those other districts, yet in 

 both deviating therefrom in the same way and in complete agreement with what 

 occurs in this respect in several other species of Euploea indigenous in that 

 island, while at the same time other species of that genus occurring in Celebes 

 as well as elsewhere do not exhibit this special modification, but resemble their 

 congeners in other islands, this can hardly be explained otherwise than by 

 attributing it to some influence operating locally in Celebes, an influence which 

 not only governs the course of colour evolution in the indigenous species but 



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