One part of Fig. 233 shows the arrangement of the caterpillars on coming out of the nest. These caterpillars are furnished with long hairs, slightly tufted, which come off with the greatest ease, and which if they penetrate into the skin, cause violent itching. In 1865 a number of the alleys of the Bois de Boulogne were shut up from the public in order to save them from this annoyance. These caterpillars construct a covering common to them all, in which they live, and transform themselves therein, each insect making for his own private use a small cocoon. This insect is said to have been found in England, but there is not sufficient evidence to admit it into our lists. [Illustration: Fig. 233.--Larvæ of the Procession Moth (_Bombyx processionea_).] [Illustration: Fig. 234.--The Vapourer Moth (_Orgyia antiqua_), male and female.] The _Orgyias_ comprise a great number of small species, of a dark colour, which do a great deal of damage to our forest trees. In September and October the male of the _Orgyia antiqua_, with his tawny wings, may often be seen flying about the streets of London. The female (Fig. 234) is remarkable, as she has only the rudiments of wings, and only goes as far as the side of her cocoon. The caterpillar of the _Orgyia pudibunda_, called also the Hop Dog, attacks almost every sort of tree. When the state of the atmosphere favours their propagation, they appear in fearful quantities, and cause the greatest havoc. During the autumn of 1828, in the environs of Phalsbourg, they were to be counted by millions. The extent of the woods laid waste was calculated at about fifteen hundred hectares. It is common in this country. [Illustration: Fig. 235.--Orgyia pudibunda.] Among the genus _Liparis_, the species of which are also very destructive to trees, we must mention the Brown-tailed Moth (_Liparis chrysorrhoea_, Fig. 236), a species by no means rare in England. The caterpillars live in quantities, on apple, pear, and elm trees, and destroy the plantations of the promenades of Paris. [Illustration: Fig. 236.--Liparis chrysorrhoea.] The females of this genus tear off the fur from the extremity of their abdomens to make a soft bed for their eggs, and to preserve them from the cold. And yet they are never to see their young, for they die after they have laid their eggs. Another tribe of _Bombycina_ contains species of a small size, which are remarkable from the habits of their caterpillars, which make, with foreign bodies, cases, in the interior of which they live and undergo their metamorphoses. The caterpillars of the genus _Psyche_ live in a case composed of fragments of leaves, of bits of grass and straw, of small sticks of wood, or of little stones, stuck together, and intermixed with silky threads. [Illustration: Fig. 237.--Case of Psyche muscella.] [Illustration: Fig. 238.--Psyche muscella.] [Illustration: Fig. 239.--Case of Pysche rubicolella.] [Illustration: Fig. 240.--Case of Psyche graminella.]