512 MR. H. W. BATES ON THE LEPIDOPTETA 



on the individuals, because, in limited districts where these conditions are the same, the 

 most widely contrasted varieties are found existing together, and it is inexplicable how 

 they could have produced the nice adaptations which these diverse varieties exhibit. All 

 the varieties figured on PI. LV. figs. 2, 7, 9, and on PI. LVI. figs. 1, 2, 3, 4, 6, are 

 found at St. Paulo, within a mUe of each other, in the same humid forest. Neither can 

 these adapted races, as before remarked, have originated in one generation by sports or a 

 sino-le act of variation in each case. It is clear, therefore, that some other active prin- 

 ciple must be here at work to draw out, as it were, steadily in certain directions the 

 suitable variations which arise, generation after generation, until forms have resulted 

 which, like our races of Leptalis Theono'e, are considerably different from their parent 

 as well as their sister forms. This principle can be no other than natural selection, the 

 selecting agents being insectivorous animals, which gradually destroy those sports or 

 varieties that are not sufficiently like Ithomice to deceive them. It would seem as 

 though our Leptalis naturally produced simple varieties of a nature to resemble 

 Ithomice ; it is not always so, as is proved by many of them figured in the places above 

 quoted. There is some general resemblance, it is true ; and this is not purely accidental ; 

 for it is quite natural that the parent Leptalis should produce offspring varying in the 

 direction of Itliomice, being itself similar to an Ithomia, and having inherited the pro- 

 perty of varying in this manner through a long line of ancestors. We cannot ascertain, 

 in this case, whether changed physical conditions have had any effect, quantitative or 

 qualitative, on the variability of the species after migrating to a new district. At any 

 rate, the existing varieties of our Leptalis show that the variations of Leptalis and 

 Ithomia are not quite coincident, and that the agency of natural selection is required to 

 bring the slowly forming race of one to resemble the other. I do not forget that at each 

 step of selection the forms of Leptalis must have had sufficient resemblance to an Itho- 

 mia to lead to their preservation, or, at least, to prevent their complete extinction : as, 

 however, the two analogues so much resemble each other at the commencement of the 

 process, these steps would not be numerous. In many cases of mimetic resemblance, 

 the mimicry is not so exact as in the Leptalides. This would show either that the imi- 

 tator has only inherited its form from remote ancestors who were actively persecuted, 

 the persecution having ceased during the career of its immediate ancestors ; or it woTild 

 show that the persecutor is not keen or rigid in its selection ; a moderate degree of 

 resemblance suflaces to deceive it, and therefore the process halts at that point. I leave 

 out of consideration all resemblances which can only be accidental, or which are resem- 

 blances of afiinity. 



If a mimetic species varies, some of its varieties must be more and some less faithful 

 imitations of the object mimicked. According, therefore, to the closeness of its persecu- 

 tion by enemies, who seek the imitator, but avoid the imitated, will be its tendency to 

 become an exact counterfeit,— the less perfect degrees of resemblance being, generation 

 after generation, eliminated, and only the others left to propagate their kind. The actual 

 state of Leptalis Theonoe is not the same in all of its three districts. A few varieties, or 

 sports, are seen at Ega (65° W. long.) and St. Paulo (69° W. long.), namely, those figured 

 PL LV. figs. 4, 5, 7, 8, and 9, which have an indeterminate resemblance. On the Cupari 



