size. They nest in hollow trees or in banks or any suitable crevice; the Trigonæ, suspend pear-shaped combs from the extremities of the branches of trees, without any kind of external Fig. 1.—Nest of Polistes. A wasp's nest without cover. covering. Meliponæ are masons and prone to block up the gap in the tree they employ with clay, leaving a small orifice for entrance and exit; some stop theirs with wax, and they incline to feed on the sweet sap that exudes from the forest trees and on the excrement of birds rather than on flowers. As with the communities of social bees, so with the social wasps (Vespidæ), there appears a third order of beings, the workers or neuters, which, like the females, are provided with a sting. The interest attached to the economy of the family rivals that of the wonderful works of the hive; indeed, many of the structures of the social wasps constitute the most beautiful examples of insect architecture. Among them there is a variety of form, an evidence of intelligent choice of the materials used in their construction, a difference of texture produced, and an adaptation of the nest to the circumstances of the situation to which the buildings of the bee can lay no claim. If the hive bee is the more admirable architect, it is decidedly not the most ingenious. It is the better mathematician, but the less facile engineer; it is the more learned, but the less imaginative. While the bees may be said to build in wax, the social wasps are chiefly natural paper or cardboard makers—not out of rags, but ligneous materials, triturated and agglutinated in various ways. Though the nests are upon many plans, essentially they are all alike. Similar cells, nearly always hexagonal, are agglomerated, leaving between them no space to form combs, after the manner of bees, but of very varying aspects. These are the cradles of the larvae, which, deposited here as eggs, are reared by the female or workers, and,