1914.] NATURAL SCIENCES OF PHILADELPHIA. 167 



there are only three forms, each one of them is mimicked. It is not 

 as if the models for mimicry were distributed indiscriminately 

 . among the butterflies. They are furnished by a few genera here and 

 there among the NymyhalincB, Pierince, etc., but the vast majority 

 of them are concentrated in the four subfamilies mentioned above 

 and in the "Aristolochia swallo\\i:ails. " Until these remarkable 

 and very numerous facts are explained by some other hypothesis 

 or until something stronger than negative evidence is forthcoming, 

 we are justified in accepting the hypothesis of advantageous resem- 

 ])lance to a specially defended model. I should be the last to rest 

 content with indirect evidence, however strong, and for many years 

 I have urged naturalists, and especially those in the tropics, to make 

 observations and to undertake experiments. As a result of much 

 work, a considerable body of direct evidence, which cannot be ignored 

 by any fair-minded opponent, has been steadily accumulating, 

 especially from x\frica; but I freely admit that more is greatly needed, 

 and I shall continue to urge my friends to seek for it. 



4. The Attempt to explain Mimetic Resemblance as due to 

 Affinity between Model and Mimic. 



Dr. Skinner appears to adopt the above interpretation of the 

 likeness between the Papilios and Pharmaco'phagus when he says 

 "The three species, glaucus, asterius, and troilus, do bear a resemblance 

 to 'philenor but this happens in any aggregation of species in a genus. " 

 (33, p. 125.) This interpretation does not bear inspection. In the 

 first place, the butterflies do not in any real sense belong to the same 

 genus, and it is for this very reason that I have provisionally adopted 

 Haase's Pharmacophagus for philenor. In the second place, the three 

 mimetic species are placed by Rothschild and Jordan in three different 

 groups of the section "Papilio" ("Fluted swallowtails"). In the 

 third place, it is clear that the true affinity is shown by the non- 

 mimetic patterns rather than by the mimetic ones — by the upper 

 surface of the male asterius and by the rtiales and glaucus females of 

 glaucus. 



Darwin suggested that mimicry began "long ago between forms 

 not widely dissimilar in color, " and Scudder adoptg the same hypothe- 

 sis in the following passage : 



"The process has been a long one, so that . . . . , we may readily 

 presume far less difference between mocker and mocked when the 

 mimicr}^ between them first began, than now exists between the 

 mocked and the normal relatives of the mocker. " (6, p. 715). It is 



