The caterpillar of this moth is one of those which we call “loopers,” because instead of walking as other caterpillars do, they hunch themselves up into a sort of loop at every step. And sometimes they are called “stick-caterpillars,” because their bodies are so like bits of twig that as long as they do not move it is very difficult indeed to see them. If you shake the branches of a tree in summer-time you will generally see several of these caterpillars swinging in the air, each at the end of a silken thread; and if you want to find that of the Swallow-tailed Moth you should look for it on willow, and lime, and elder, and pear trees. When it is fully grown it spins a cocoon just like a little hammock, and turns to a light brown chrysalis spotted with black. [Illustration: PLATE XXXIV 1. Swallow-tail Moth 2. Swallow-tail Caterpillar 3. Emperor 4. Emperor Caterpillar] PLATE XXXIV THE EMPEROR (3 and 4) This is one of the handsomest of all our British moths, and the caterpillar is even more beautiful than the moth. For it is of the brightest apple-green colour, with ten or eleven velvety-black rings round its body; and every ring has a number of raised pink spots upon it, with six black bristles springing from each spot, and spreading outwards in the form of a star. You may often find it on bramble-leaves early in September, and it also feeds on blackthorn, willow, and heath. When this lovely caterpillar has reached its full size, it spins a most curious cocoon, shaped something like a little flask, with a number of bristles inside the entrance arranged in such a way, that while the moth can crawl out quite easily when it is ready to hatch, none of its enemies can crawl in. In this cocoon the chrysalis lies all through the winter, and the moth makes its appearance in April, when you may often see it flying about in the sunshine on heaths and commons. The male is rather smaller than the female, and you can always recognise him by his brighter colouring, and his beautifully plumed feelers. PLATE XXXV THE BRIMSTONE MOTH (1)