Mimetic Analogy. 311 



Among the most numerous butterflies of this South Ameri- 

 can region are various genera and species belonging to the 

 family of HeliconidaB. The species, wherever they occur, are 

 described by Mr. Bates as being exceedingly abundant in in- 

 dividuals ; they show signs of flourishing existence, although 

 of slow flight and feeble structure, and apparently unfurnished 

 with any means of defence, although living in districts 

 abounding with insect-eating birds. So numerous are they 

 that the pathways in the forests are rendered gay with the 

 multitudes that fly about among the trees in their bright 

 dresses of orange, blue, yellow, red, and black. Some species 

 of these fine showy butterflies are described by him as assem- 

 bling together in small parties like our gnats, or by twos and 

 threes, to sport together and perform a kind of mazy dance. 

 The sport generally begins with a single pair ; they advance, 

 retire, glide right and left in face of each other, wheel round to a 

 considerable distance, again approach, and so on ; then a third 

 joins in, and then a fourth, and so on, until a large party is assem- 

 bled. They never touch ; but when too many are congregated 

 a general flutter takes place, and they all fly off to fall in again 

 by pairs shortly afterwards. 



It is noticed that wherever large numbers of any of these 

 Heliconidge abound, they are always accompanied by species 

 which closely mimic them in size, form, colour, and marking ; 

 and these resemblances are so close that it is often impossible 

 to distinguish one species from the other when they are on the 

 wing, as the imitators fly in the same part of the forest, and go 

 usually in company with the species they imitate. To so won- 

 derful an extent is this imitation carried, that, in cases where 

 there is a local variety of a species of the family Heliconidse, 

 the butterfly imitating that particular species changes so as to 

 follow the variations of its model. 



It maybe asked if two butterflies, of totally distinct groups, 

 and having different structures, thus closely resemble one 

 another, how can it be known which is the imitator and 

 which the imitated ? The answer to this question is suffi- 

 ciently easy. The objects imitated preserve the form and 

 likeness peculiar to the family to which they belong ; but the 

 imitators are of a different aspect to their nearest allies. Thus 

 when a clear- winged moth is found, having a close resemblance 

 to any species of bee, we have no hesitation in saying that the 

 moth, having departed from "the usual aspect of its group, has 

 imitated the bee, which remains like its congeners, and not 

 that the bee has imitated the moth. Or, to take the examples 

 shown in our coloured plate, we are justified in assuming that 

 the different species of Leptalis, shown in the Figures 2, o, and 

 4 in our coloured plate, are the imitators, because they have 



