Now in the case of some of these spiders the chance of obtaining a meal is very greatly increased by a remarkable similarity of coloration between the spider and its usual hunting ground. The spider’s object is to remain invisible, and concealment is obviously more easy if its colour matches that of its environment. To a greater or less extent this protective coloration as it is called prevails universally:—spiders are seldom conspicuous objects among their usual surroundings, but it is only occasionally that we meet with cases of very remarkable colour adaptation. Two such, however, occur among English crab-spiders. One is a species not uncommon in the south of England, and fairly plentiful in the New Forest, where it is to be sought among the lichen on the tree trunks, where its blue-grey body, marked with black and white blotches makes it practically invisible except when in motion. It rejoices in the name of _Philodromus margaritatus_. The other case is that of the spider known as _Misumena vatia_, which is variable in colour, some specimens being yellow and others pink, while a variety of the species has a blood-red streak decorating the front part of its abdomen. If it were to choose lichen as a hunting ground there would be little chance of concealment, but it does nothing so foolish:—it hides among the petals of flowers, generally, but not always, among flowers more or less of its own colour. Now this phenomenon of resemblance is sometimes carried very much farther than a tolerable correspondence between the colour of an animal and its surroundings; it occasionally amounts to an apparent imitation, in form and in behaviour as well as in colour, of some other object, either animal or vegetable and in such cases we have examples of what is known as Mimicry. Most people have seen remarkable instances of this phenomenon in the “stick” and “leaf” insects of entomological collections. There are several different ways in which such a resemblance may be profitable to the imitator. Clearly it may be advantageous for a weak animal to be mistaken for one much more formidable and less likely to be attacked, or for an insect which is really extremely good eating to resemble closely one which birds well know to be unpalatable. Or again, if your line is to lie _perdu_ and wait for some unwary insect to come within reach, it must be a distinct asset to be indistinguishable from such an innocent object as a twig or a leaf; and the same disguise may serve you if you are the possible victim and you can make the would-be devourer believe that you are a mere vegetable.