The cocoon of the emperor-moth, which has already been described, is made on the same principle. There are several caterpillars which are social in their early stages, and which construct a common habitation. The Little Ermine-moth. (Hyponomeuta padella) affords a familiar example of this structure. The caterpillars are great roamers in search of food by day, and travel from branch to branch on their strong silken threads. At night, however, they return to a large white silken habitation which they have spun, and which they divide into many compartments, as may easily be seen by cutting the nest open with very sharp scissors. Within this habitation the caterpillars spin their separate cocoons, so that the system of double walls is thoroughly carried out. There is another insect, very common on the Continent, but, happily for us, not introduced into England. It is called the Processionary Moth, from its curious habit of marching in exact lines, the head of the second caterpillar touching the tail of the first, and so on. These insects have likewise a common home, and spin their own separate cocoons within it. * * * * * [Illustration: NEST OF PROCESSIONARY MOTH.] [Illustration: COCOON OF SILK-WORM.] [Illustration: FIREPROOF SAFE.] There are two other sociable British Moths which make nests on a similar principle. These are the Gold-tailed Moth (_Porthesia chrysorrhœa_) and the Brown-tailed Moth (_Porthesia auriflua_). They are both beautifully white insects, but may easily be distinguished from each other, the Gold-tailed Moth having some brown-black spots on the upper wings, and a tuft of golden-yellow hairs at the end of the body; while the Brown-tailed Moth is without spots, and the tail-tuft is brown. In habits they are very similar, and the description of the nest made by one will answer for that made by the other. I believe that broods of these two species have been known to construct a common nest. The nest is extremely variable in form, because it depends much on the number of twigs which it includes. Interiorly, it is divided into a considerable number of chambers, each containing one or several individuals. As the caterpillars are hatched late in summer, they have to undergo the frosts of winter before they can attain their perfect state. Accordingly, before the winter-time comes on, they strengthen both the external walls and internal partitions of their nest, and then wait until the spring brings forth the leafage of the new year. The nest is a beautiful structure, and I strongly recommend the reader to look for one in a hedgerow, take it home, and cut it up carefully. I would, however, advise him, if, like myself, he be subjected to a very sensitive skin, to be cautious in his handling of the nest. The hairs with which the pretty black, red, and white caterpillars are studded are irritant in the extreme.