Page:Popular Science Monthly Volume 42.djvu/204

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THE POPULAR SCIENCE MONTHLY.

tropics, once related to me an experience of his in the West Indies, that throws light upon another phase of snail life, and reminds one of precisely similar incidents among the Lepidoptera. This naturalist had a habit of holding small snails in his mouth when collecting upon cliffs or trees where climbing was difficult. The light or dull colored species of Cylindrella, Helicina, etc., caused him no inconvenience, but the snails with conspicuously bright and shining shells, such as occur in the groups Streptostyla and Varicella, were so intensely bitter that he soon learned to let them remain unless he could carry them elsewhere. It is reasonable to conclude that birds find them equally unpalatable. The facts, as far as they are known, seem to indicate that this is an example of "warning coloration," such as many conspicuous but nauseous butterflies possess.

It may be remarked that the custom of holding specimens between the lips is not so rare with field naturalists as fastidious persons might suppose. I confess to having once swallowed a small and very rare specimen while so holding it for a moment. The creature was, alas! not my own property, and its outraged owner has not yet forgiven me.

A protective device totally different in kind from those just described has been observed in certain slug-like snails, which have the ability to amputate their own tails, just as a lizard does when seized by that appendage. Dr. Carl Semper has noticed this peculiarity in snails of the genus Helicarion, in the Philippine Islands; and a species of the genus Prophysaon, of California, has lately been seen to lose its tail in the same manner.[1]

PSM V42 D204 Indian snail atopa achatina.jpg
Fig. 4.—An Indian Snail, Atopa achatina. Broken, to show the internal folds.

It is probable that the explanation is the same in the case of both lizards and snails—viz., the tail is likely to be the part seized by an enemy just as the escaping creature is disappearing into a sheltering crevice. The advantage of saving the head, even at the expense of the tail, is obvious.

Protective coloring and protective resemblance are, however, a defense only against the larger enemies of the mollusk, which hunt their game in the open, such as birds, field-mice, and incidentally, conchologists. But, besides these, snails have smaller foes which meet them upon their own ground. The omnipresent Insecta are


  1. See article by W. J. Raymond, Why does Prophysaon shed its Tail? The Nautilus, May, 1890.