_Section 2.--Diploptera._ _Family 3, Vespidæ._--The Social Wasps, which belong to this family, are very well known everywhere in this country. In their general structure they resemble the bees, but are usually much more slender in appearance, and also much less hairy. [Illustration: Fig. 17.--Polistes Gallica.] The general habits of these wasps are pretty uniform except in the matter of their architecture, and in this respect they display a remarkable variety. [Illustration: Fig. 18.--Nest of Polistes Gallica.] Besides the common Wasp (_Vespa vulgaris_) two other species found in this country, which build their nests in the ground, follow the same principles in the construction of their nests. The Hornet (_Vespa crabo_), which is remarkable for its large size, usually builds its nest in the hollow of a tree. Both the hornet and common wasp sometimes build their nests under the eaves of houses or attached to a beam under the roof; and in these cases the outer covering of the nest is thinner and more delicate in texture than when the dwelling is exposed to the vicissitudes of the weather. Another common species inhabiting Britain is the Wood Wasp (_Vespa sylvestris_), which builds nests suspended from the branches of trees. [Illustration: Fig. 19.--Odynerus Ovalis (Mag.)] _Family 4, Eumenidæ._--One of the commonest and best-known species belonging to this family is the Wall Wasp (_Odynerus parietum_), which may be almost constantly seen haunting sunny walls during the months of June and July. It makes its burrows in walls and high banks, while many other allied species form their nests in the hollow stems of brambles. _Family 5, Masaridæ._--This family contains the great bulk of the solitary wasps, which, however, are principally inhabitants of warm climates. The _Masaridæ_ are a small group of black-yellow belted wasps, which are found in the south of Europe, but not in Britain, two of the commonest species being _Celonites apiformis_ and _Ceramius fonscolombi_. _Section 3.--Fossores._ [Illustration: Fig. 20.--Cerceris Capito.] _Family 6, Philanthidæ._--Most of the species belonging to this family are black with yellow spots and bands, and most of them are inhabitants of the warmer parts of the earth. Some of the species provision their nests with beetles and grasshoppers, while others attack bees, and are very mischievous, destroying great numbers. _Family 7, Crabronidæ._--This family includes a considerable number of solitary species of wasps. In colour they are generally black spotted and striped with yellow, but many of them are bright red. The typical genus _Crabro_ is a very extensive one, including over 150 species, a great proportion of which are inhabitants of Europe, while even Britain possesses more than thirty.