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number of other butterflies ; they resorted to the forest shades only towards evening or 
on cloudy days. The cause of the female of Pieris Pyrrha having been brought to 
resemble a Heliconid butterfly was the same as that which had drawn ont the 
wonderful mimetic dress of the Leptalides; namely the protection which such 
resemblance affurded them against the persecutions of insectivorous animals. A more 
remarkable case than Pieris Pyrrha was that of Papilio Torquatus, a well-known 
Brazilian butterfly, of light yellow and black colours (in the male). Like the male of 
Pieris Pyrrha, Papilio Torquatus (male) spent his days in the open sunshine, whilst 
the female was confined to the shades of the forest, flying heavily and depositing her 
eggs one by one underneath the leaves of low trees. The female offered the most 
striking contrast in colours to the male, being black with white spots and crimson 
macular belt. It was significant that the dominant forms of Papiliones of the forest 
shades of tropical America had precisely that style of coloration; but the importance 
of the present case lay in this, that the female Torquatus presented local varieties in the 
various regions inhabited by the species, the male remaining unchanged, and the 
varieties were adapted in dress to the species of the dominant Aineas group peculiar to 
the localities. ‘Thus on the Lower Amazons the form of the female was that which 
had been named P. Candius by Hubner, having a white spot on the fore wing, and 
a crimson belt on the hind wing, precisely as in the females of the common species 
inhabiting the same region, e.g. P. Aineas, P. Parsodes, P. Echelus, P. Ergeteles, &c. 
On the Upper Amazons, the female was very variable, but the commonest varieties 
resembled closely the females of the species of the Aineas group most prevalent there, 
namely, P. Lysander and P. Bolivar: the resemblance to the female Bolivar was most 
extraordinary, for in that species the crimson macular belt was replaced by yellow. 
Mr. Bates also made some remarks in auswer to the objections which Professor 
Westwood had urged against the explanation of these imitative analogies on Darwinian 
principles. He said that the case of the Leptalides published by him could not, in 
his opinion, be explained in any other way. The species of Leptalis in question was 
found in several distant localities; in some of them it existed under one constant 
local form only, in others it was exceedingly variable, the common varieties showing a 
wonderful tendency towards a likeness to the predominant species of Ithomia of the 
respective localities. Ifthe dress now worn by the Leptalis was given it at its creation, 
as Professor Westwood believed, how would he explain all these numerous shades of 
variety found in one and the same locality? To be consistent he must say that each 
variation was lineally descended from an originally created variety, which would be 
absurd, as so many species are known to offer numerous similar varieties in one and the 
same brood. As some of these varieties of Leptalis resembled species of Ithomia 
peculiar to the locality more than their sister varieties did, the conclusion was simple 
and natural, that, the imitation being a rule in all other localities, the process was there 
at work by which the close imitation was brought about. The less exact imitations 
were in course of time destroyed without bringing forth progeny, and then the state of 
things was identical with what was found in other localities, namely, one or more 
constant forms of Leptalis resembling closely their companion Ithomiz. 
Dr, Sharp remarked that whether the resemblances under discussion were purely 
accidental or not could be determined by a numerical investigation, by ascertaining 
what proportion the cases in which species resembling one another occurred in 
company bore to the cases in which species with a similar amount of resemblance 
