‘Protective’ Adaptations of Animals

Abstract

ON the subject of “ant-mimicry” Mr. Uvarov states¹ on McAtee's authority, “that more than three hundred species of American birds (out of the total number of about eight hundred species including non-insectivorous ones) feed on ants and some of them consume thousands of individuals.” He does not seem to have noticed the consequences of McAtee's method in tabulating “the total number of identifications...from these stomachs, counting those of whatever degree, once for each time identified, irrespective of the number of individual specimens concerned”² (p. 7). Therefore a bird's stomach containing a single ant or a very small number, liable to be swallowed accidentally with other food, would lead to the obviously absurd conclusion that the bird feeds on ants. A woodpecker's stomach containing 2,000 ants (p. 93) supplies evidence which, on this system, is of no greater value than a stomach containing a single ant. It is much to be regretted that McAtee, with all this vast material before him, did not publish all the available data which would have enabled us to know more of the real and habitual enemies of ants as well as of other insects. Mr. H. B. Cott has done this work admirably in his paper³ on the tree—frogs of the Lower Zambezi. Here we are given incontrovertible evidence that certain species regularly feed upon these powerful and aggressive insects. But who doubts that they have many enemies ? Yet it will, I think, be clear to anyone who reads Mr. C. Elton's interesting paper on “Territory among Wood Ants”, that insects mistaken for ants in Dr. T. G. Longstaff's bird sanctuary at Picket Hill would, on the whole, be benefited by the resemblance and that the chance of being eaten as an ant by the green woodpecker would be a risk well worth taking.