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the two species of Heterocera, the two Nymphalidae and the two Hesperidae, 

 feed on the leaves of the same plant, I think I am justified in looking upon 

 this as the cause of the great similarity of these larvae. I do not mean to 

 say that the food itself could directly have changed colour or form, but that the 

 ancestors of these larvae originally probably left another food for that on which they 

 feed now, and that this change has given a particular direction to their further 

 development, which has consequently moved along the same line in both species, 

 especially if they were already closely allied, and has thus given them such a striking 

 resemblance. Whether this explanation of those remarkable convergency-phenomena 

 is correct can only be decided at some future time. As for me, I do not know a better 

 one ; for to the e.xplanation of the Mimicry theory I attach no importance. 

 But to be able to judge mine, it is of course necessary that one has first 

 learned to understand the nature of the phenomenon of evolution in general. 

 There are among the European fauna two Heterocera in which something 

 similar occurs, the two moths Acronycta Psi L. and A. Tridens W. V., 

 belonging to the same genus and hence closely connected. Though entomologists 

 have tried to take for granted a constant difference between these two 

 species, the attempt seems to have failed, for only individual differences seem 

 to have been looked upon as such. So able a connoisseur of those 

 fauna as my collaborator, Mr. Snellen, has declared to me that he is not 

 able to distinguish the imagines of the two species with any certainty. But on 

 the other hand, in the case of their larvae the difference is very clear and they 

 do not live on the same feeding-plants. In accordance with the above theory 

 the explanation might be, that the two species have sprung from one and the 

 same primitive species, whose larvae fed on the same, or closely allied, species 

 of plants, but that then, in consequence of certain circumstances unknown to 

 us, a part of those larvae began to feed on other plants, so that two species 

 have developed, whose difference, however, only appears as yet in the form 

 and the colour of the larvae. For it is well known that the evolutional change 

 of larva, pupa and imago continues independently, so that in different species 

 the old form of the larva has remained, though the imago has already assumed 

 a new form. Thus the larvae of Papilio Aristolochiae F. and P. Coon F. 

 still show the same form that is peculiar to the larvae of Ornithoptera from 

 which they have descended, through the imagines are no longer Ornithoptera 

 but must be classed under the genus Papilio. And so as been mentioned in the 

 treatise on the Pieridae, part of the larvae of Callidryas Pomona F. still have 

 the old colour, similar to that of the larvae of C. Scylla L. though from them, 

 too, the imagines of the first mentioned species always originate. Between 

 the larvae of Cupha Erymanthis Did. and Atella Sinha KoUar, both living 



