Green parrots fly over in screaming flocks, or nestle in loving couples amidst the foliage, toucans hop along the branches, turning their long, highly-coloured beaks from side to side with an old-fashioned look, and beautiful tanagers (Ramphocaelus passerinii) frequent the outskirts of the forest, all velvety black, excepting a large patch of fiery-red above the tail, which renders the bird very conspicuous. It is only the male that is thus coloured, the female being clothed in a sober suit of greenish-brown. I think this bird is polygamous, for several of the brown ones were always seen with one of the red-and-black ones. The bright colours of the male must make it very conspicuous to birds of prey, and, probably in consequence, it is not nearly so bold as the obscurely-coloured females. When a clear space in the brushwood is to be crossed, such as a road, two or three of the females will fly across first, before the male will venture to do so, and he is always more careful to get himself concealed amongst the foliage than his mates. I walked some distance into the forest along swampy paths cut by charcoal burners, and saw many beautiful and curious insects. Amongst the numerous butterflies, large blue Morphos and narrow, weak-winged Heliconidae, striped and spotted with yellow, red, and black, were the most conspicuous and most characteristic of tropical America. Amongst the beetles I found a curious longicorn (Desmiphora fasciculata), covered with long brown and black hairs, and closely resembling some of the short, thick, hairy caterpillars that are common on the bushes. Other closely allied species hide under fallen branches and logs, but this one clung exposed amongst the leaves, its antennae concealed against its body, and its resemblance to a caterpillar so great, that I was at first deceived by it. It is well known that insectivorous birds will not touch a hairy caterpillar, and this is only one of numberless instances where insects, that have some special protection against their enemies, are closely imitated by others belonging to different genera, and even different orders. Thus, wasps and stinging ants have hosts of imitators amongst moths, beetles, and bugs, and I shall have many curious facts to relate concerning these mimetic resemblances. To those not acquainted with Mr. Bates's admirable remarks on mimetic forms, I must explain that we have to speak of one species imitating another, as if it were a conscious act, only on account of the poverty of our language. No such idea is entertained, and it would have been well if some new term had been adopted to express what is meant. These deceptive resemblances are supposed, by the advocates of the origin of species by natural selection, to have been brought about by varieties of one species somewhat resembling another having special means of protection, and preserved from their enemies in consequence of that unconscious imitation.