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brown hue being of a shade that assimilates very closely to the surroundings. There are pale yellowish browns, lined and mottled, in species living amidst a sere, scanty vegetation; earthy browns, in those frequenting open sterile or stony places; while the species that creep on trees in forests are dark brown in colour, and in many cases the feathers are mottled in such a manner as to make them curiously resemble the bark of a tree. The genera Lochmias and Sclerurus are the darkest, the plumage in these birds being nearly or quite black, washed or tinged with rhubarb yellow. Their black plumage would render them conspicuous in the sunshine, but they pass their lives in dense tropical forests, where the sun at noon sheds only a gloomy twilight.
If "colour is ever tending to increase and to appear where it is absent," as Dr. Wallace believes, then we ought to find it varying in the direction of greater brightness in some species in a family so numerous and variable as the Dendrocolaptidae, however feeble and in need of a protective colouring these birds may be in a majority of pases. And this in effect we do find. In many of the dark-plumaged species that live in perpetual shade some parts are a very bright chestnut; while in a few that live in such close concealment as to be almost independent of protective colouring, the lower plumage has become pure white. A large number of species have a bright or nearly bright guiar spot. This is most remarkable in Synallaxis phryganophila, the chin being sulphur-yellow, beneath which is a spot of velvet-black, and on either side a white
2 5O The Naturalist in La Plata.
patch, the throat thus having three strongly contrasted colours, arranged in four divisions. The presence of this bright throat spot in so many species cannot very well be attributed to voluntary sexual selection, although believers in that theory are of course at liberty to imagine that when engaged in courtship, the male bird, or rather male and female both, as both sexes possess the spot, hold up their heads vertically to exhibit it. Perhaps it would be safer to look on it as a mere casual variation, which, like the exquisitely pencilled feathers and delicate tints on the concealed sides and under surfaces of the wings of many species possessing outwardly an obscure protective colouring, is neither injurious nor beneficial in any way, either to the birds or to the theory. It is more than probable, however, that in such small feeble-winged, persecuted birds, this spot of colour would prove highly dangerous on any conspicuous part of the body. In some of the more vigorous, active species, we can see a tendency towards a brighter colouring on large, exposed surfaces. In Auto-malus the tail is bright satiny rufous; in Pseudo-colaptes the entire under surface is rufous of a peculiar vivid tint, verging on orange or red; in Magarornis the bosom is black, and beautifully ornamented with small leaf-shaped spots of a delicate straw-colour. There are several other very pretty birds in this homely family; but the finest of all is Thripodectes flammulatus, the whole body being tortoise-shell colour, the wings and tail bright chesnut. The powerful tanager-like beak of this species seems also to show that it has diverged
The Woodhewer Family. 251
from its timid shade-loving congeners in another direction by becoming a seed and fruit eater.