Page:The Zoologist, 4th series, vol 3 (1899).djvu/497

Rh thesis that supposing certain caterpillars not very particular as to their food, either Elm, Lime, Birch, &c, and further assuming that such caterpillars were more easily overlooked on Birch by resembling the catkins of that tree, then those broods which fed on trees other than Birch would be most likely to be devoured by enemies, and so gradually a race would grow up which invariably fed on Birch.

The active mimicry here discussed does not deal with the mimicking by birds of the songs of their fellows. This imitative faculty had been recorded of birds in captivity by Aristotle. But in a state of nature the same thing occurs. Mr. Butterfield has narrated his having heard a Whinchat, a bird of no extensive vocal capacity, imitate "in quick succession the song of the Wren, Song Thrush, Chaffinch, Corn Bunting, Tree Pipit, Greenfinch, and Starling." Mr. Riley Fortune has known the Starling to give perfect imitation of the cries of the Sparrow, Lapwing, Golden Plover, Chaffinch, Blackbird, Yellowhammer, Thrush, Jackdaw, Swallow, and many other birds. Prof. Lloyd Morgan is of opinion that "mimetic activities are due to a mimetic impulse. Some of them are probably involuntary and due to connate impulse; but others are certainly due to intelligent imitation." Thus Lumholtz, in Queensland, observed the mental process in the Lotus-bird (Parra gallinacea): "The grown bird is not shy, but the young are extremely timid. I had once or twice seen the old birds with young, but as soon as I approached them the young always disappeared, while the old birds walked about fearlessly, as if there was no danger. It long remained a mystery to me how they could conceal themselves so well and so long, but one day the problem was solved. An old bird came walking with two young ones near shore. I hid behind a tree and let them come close to me. As I suddenly made my appearance, the small ones dived under the water and held themselves fast to the bottom, while I watched them for a quarter of an hour before