OF THE AMAZON VALLEY. 505 



Ithomia of the locaKty being thus changed, how stands it with the LepUdides ? They 

 are changed also, and again with close reference to the Ithomice. I found a number of 

 different varieties, which I could not doubt Avere local forms of the same species as that 

 found on the Cupari and at Ega. Thus, there was one (PI. LV. fig. 2) closely resembling 

 L. Theonoe (fig. 1), but modified to produce a nearer imitation of the Ithomia Onega 

 (PI. LV. fig. 2 a), which I believe to be a local form of J. Flora. Another (PI. LVI. fig. 3) 

 resembled Ithomia Chrysodonia (PL LVI. fig. 3 a) ; but the imitation is not fixed or exact 

 in aU the specimens taken, as may be seen by comparing figs. 1, 2, 3, of the same Plate. 

 We here detect nature, as it were, striving after a correct imitation : the explanation of 

 this will be attempted further on. A third form of Leptalis found at St. Paulo is the 

 one figured PI. LVI. fig. 6, which munics the Ithomia Virginia (PL LVI. fig. 6«). 

 Besides these, a few varieties occurred which did not closely counterfeit any Ithomia ; 

 they were very much rarer than the others. I figure two of these (PL LV. figs. 7, 9), to 

 show how they connect the other more strongly modified varieties with the Ega forms. 



The IthomicB concerned in these imitations have the character of true species, being 

 distinct and constant, with the excejotion of I. Chrysodonia, whose varieties are detailed 

 under the head of the species, which is variable, and throws light on the origin of the 

 rest. They are all excessively numerous in individuals, swarms of each kind being found 

 in the localities they inhabit. The Leptalides are exceedingly rare ; they cannot be 

 more than as 1 to 1000 with regard to the Ithomice. It may be asked, how can we know 

 they are all varieties (using the term as meaning forms descended from others) of one 

 species ? I must refer to the figures given, which, although they do not include all the 

 connecting varieties that were collected, show how nearly all the forms are linked to- 

 gether. The most distinct amongst them are those figured PL LVI. figs. 4 and 6. The 

 feature which distinguishes fig. 4 is the white colour of the disk of the hind wings, and 

 the veins which traverse it. This character is shown to be due to variation, from the 

 facts that Ithomia Oncidla, an undoubted variety of J. Chrysodonia (or Orolina), exhibits 

 a commencement of this milky shade of the Avings, and that many individuals of I. Iler- 

 dina (PL LVI. fig. 4 a) display steps of modification in the colours of the veins. The 

 variety figured PL LVI. fig. 6, appears distinct, from the single pale spot near the tips of 

 the wings ; an approximation to this is seen in the variety figured PL LV. fig. 9, which 

 is an undoubted modification of L. Lysinoe (PL LV. fig. 3). The remarkable variety 

 figured PL LV. fig. 4 has been described by the only author who has treated on these 

 insects (Mr. Hewitson) as a variety of L. Lysinoe. In a polymorphic form, like this 

 Leptalis, none of the varieties can be taken from the rest and denominated species, 

 (using the term as meaning forms which cannot have descended from other closely allied 

 ones), without exercising the art of species-making in the most arbitrary manner. For if 

 we allow so great a latitude to variation as that from figs. 3 to 4, 5, 6, 7, 8, and 9, PL LV., 

 how can we venture to say that natural modification, having gone so far, was incompetent 

 to go further, so as to produce figs. 4 and 6, PL LVI., and that those forms must have 

 arisen by some unknown agency ? It is true, they have not arisen by simple variation, 

 or sports, in one generation, but, as we shall presently see, by an external agency 

 accumulating the modifications of many generations in two diverging directions. As 



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