[99] "Mémoires pour servir à l'Histoire des Insectes," tome ii., p. 765. In 4to. Stockholm, 1771. [Illustration: Fig. 347.--The Hornet (_Vespa crabro_).] Wasps collect the materials with which they build near the place where they have chosen to establish their domicile. These materials are ligneous fibre, mixed up with saliva, with the aid of which these insects prepare the paper-like substance, which is very tough, and destined to form the walls of the cells and their exterior covering. The greater number make their habitation in the ground. Of these is our Common Wasp (_Vespa vulgaris_), which is black, agreeably contrasted with bright yellow. The Bush Wasp (_Vespa norvegica_), which inhabits woods, constructs its nest between the branches of shrubs or bushes. It is smaller than the common species. The Hornet is the largest European species of the family of the _Vespidæ_. The substance of its nest is yellowish, and very fragile, and is constructed under a roof, in a loft, or in the hole of an old wall, but most often in the hollow of a decayed tree. Another species of this family (_Polistes gallica_, Fig. 348) fixes its little nest by a footstalk to the stem of some plant. [Illustration: Fig. 348.--Polistes gallica.] Wasps begin laying in spring, and go on laying all the summer. Each cell receives one single egg, and, as with bees, the workers' eggs are the first laid. Eight days after the laying, there comes out of each egg a larva without feet, and already provided with two mandibles. These larvæ receive their food in the form of balls, which the females or the workers knead up with their mandibles and their legs before presenting to their nurslings, very nearly in the same way as birds give their beak full of food to their little ones. At the end of three weeks the larvæ cease to take food, and begin to shut themselves up in their cells, the interior of which they line with a coating of silk. In this they change their form, and assume the appearance of the perfect insect, with its six legs and its wings, but motionless, and contracted together. A sort of bag keeps all the organs swathed up together (Fig. 349). This pupa state lasts for eight or nine days, at the end of which time the insect is fully developed; it casts its skin, breaks the door of its prison, and launches itself into the air. A cell is no sooner abandoned than a worker visits, cleans it, and puts it in a fit state to receive another egg. [Illustration: Fig. 349.--Pupa of the common wasp.] During the summer the female wasp remains constantly in the nest, absorbed with family cares. She is occupied in laying eggs and in feeding her progeny, with the active assistance of the workers, or mules, as Réaumur and Charles de Geer call them, because they are unfruitful.