514 iMR. H. W. BATES ON THE LEPIDOPTERA 



have a real affinity, the genera to which they belong being throughout very similar in 

 colours and markings, and all equally flourishing, to the similar adaptation of all to the 

 same local, probably inorganic, conditions. The selecting agent, which acts in each 

 locality by destroying the variations unsuitable to the locality, would not in these cases 

 be the same as in Leptalis ; it may act, for anything we know, on the larvae ; in other 

 respects, however, the same law of nature appears, namely, the selection of one or more 

 distinct varieties by the elimination of intermediate gradations *. The conditions of life 

 of these creatures are different in each locality where one or more separate local forms 

 prevail, and those conditions are the selecting agents. With regard to the Lej)talides, 

 I believe we may be said to know these conditions. To exist at all in a given locality, our 

 Leptalis Theonoii must wear a certain dress, and those of its varieties which do not come 

 up to the mark are rigidly sacrificed. Our three sets of Leptalides may be compared to 

 a variable flowering plant in the hands of a number of floriculturists, whose aims are dif- 

 ferent, each requiring a different colour of flower, and attaining his end by " roguing" 

 or destroying all variations which depart from the standard. 



It may be remarked that a mimetic species need not always be a rare one, although 

 this is very generally the case ; it may be highly prolific, or its persecution may be in- 

 termitted when the disguise is complete. 



The operation of selecting agents, gradually and steadily bringing about the deceptive 

 resemblance of a species to some other definite object, prodiices the impression of there 

 being some innate principle in species which causes an advance of organization in a 

 special direction. It seems as though the proper variation always arose in the species, 

 and the mimicry were a predestined goal. This suggested the only other explanations 

 that I have heard of, namely, that there may be an innate tendency in the organization 

 to become modified in a given direction — or that the parent insect, being powerfully 

 affected by the desire of concealment from the enemies of its race, may transmit pecu- 

 liarities to its offspring that help it to become modified, and thus, in the course of 

 many generations, the species becomes gradually assimilated to other forms or objects. 

 On examination, however, these explanations are found to be untenable, and the appear- 

 ances which suggest them illusory. Those who earnestly desire a rational explanation, 

 must, I think, arrive at the conclusion that these apparently miraculous, but always 



* Some of the close resemblances amongst the Ileliconida; themselves seem to be kept up by their varying in a 

 precisely similar way. There is a very singular instance in three species of three different genera, Melinaa, Mecha- 

 nitis (Mothone), and Helkoniiis, which are all, in East Peru, orange and black in colour, and in New Granada 

 orange, black, and yellow. This seems to be a case of coincident, simple variation ; for if three forms are quite alike 

 in colours, it is conceivable that they may vary alike when placed under new conditions by migration. Our Lepta- 

 lides have been shown not to vary precisely like their models ; and therefore the case just quoted does not throw any 

 difficulty in the way of the explanation 1 have given ; but it is a very extraordinary one. 



I have not thought it necessary to mention cases of close resemblances in insects which are only accidental, or which 

 are explicable by the blood- relationship or affinity existing between the species which display them. Some orders of 

 insects contain an almost infinite variety of forms, and it will not be wonderful, therefore, if species here and there 

 be found to resemble each other, although inhabiting opposite parts of the earth, and belonging to widely different 

 families. Such analogies are accidental, and can have nothing at all to do with the evidently intentional system 

 of resemblances, carried on from place to place, which I have discussed! Some cosmopolitan families present very 

 similar species in all parts of the earth ; it can scarcely be necessary to say that close resemblances between New and 

 Old World forms in these cases are resemblances of affinity, and not mimetic analogies. 



