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Protective Resemblances in Spiders: Cyrtarachne

The following account of a spider which mimics a snail-shell is given by Mr. G. F. Atkinson: - "An undescribed species of Cyrtarachne mimics a snail-shell, the inhabitant of which, during the summer and fall, is very abundant on the leaves of plants in this place. In the species of Cyrtarachne the abdomen partly covers the cephalothorax, is very broad at the base, in this species broader than the length of the spider, and rounds off at the apex. When it rests upon the under side of a leaf with its legs retracted it strongly resembles one of these snail-shells by the color and shape of its abdomen. The two specimens which I collected deceived me at first, but a few threads of silk led me to make the examination. The spider seemed so confident of its protection that it would not move when I jarred the plant, striking it several hard blows. Protective Resemblances in Spiders 363 I pulled the spider forcibly from the leaf, and it did not exhibit any signs of movement until transferred to the cyanide bottle."

Trimen gives an account of the imitation, by spiders, of horseflies, a case falling into Class 2, as follows: - "Hunting spiders are in some cases very like their prey, as may everywhere be noticed in the case of the species of Salticus which catch horseflies on sunny walls and fences. The likeness is not in itself more than a general one of size, form and coloring; but its effect is greatly aided by the actions of the spider, which walks hurriedly for short distances, stopping abruptly, and rapidly moving its falces, in evident mimicry of the well-known movements so characteristic of flies."

Instances of spiders mimicking ants are very numerous, and in many cases the resemblance is so close as to, at first sight, deceive a trained naturalist. This resemblance is brought about by the spider's body being elongated and strongly constricted, so that it appears to be composed of three segments instead of two, by the color, by the way in which the spider moves about, zigzagging from side to side like an ant, and by its habit of holding up one pair of its legs and moving them in such a way that they look exactly like the antennæ of an ant.