Page:The naturalist on the River Amazons 1863 v1.djvu/324

 genera. Thus, on the Upper Amazons, another totally distinct kind of Agrias mimicks still more closely another Callithea; both insects being peculiar to the district where they are found flying together. Resemblances of this nature are very numerous in the insect world. I was much struck with them in the course of my travels, especially when, on removing from one district to another, local varieties of certain species were found accompanied by local varieties of the species which counterfeited them in the former locality, under a dress changed to correspond with the altered liveries of the species they mimicked. One cannot help concluding these imitations to be intentional, and that nature has some motive in their production. In many cases, the reason of the imitation is sufficiently plain. For instance, when a fly or parasitic bee has a deceptive resemblance to the species of working bee, in whose nest it deposits the egg it has otherwise no means of providing for, or when a leaping-spider, as it crouches in the axil of a leaf waiting for its prey, presents an exact imitation of a flower-bud; it is evident that the benefit of the imitating species is the object had in view. When, however, an insect mimicks another species of its own order where predaceous or parasitic habits are out of the question, it is not so easy to divine the precise motive of the adaptation. We may be sure, nevertheless, that one of the two is assimilated in external appearance to the other for some purpose useful,—perhaps of life and death importance—to the species. I believe these imitations are of the same nature as those in which an insect or lizard is coloured and marked