[Illustration: Fig. 28—Nidification of solitary wasps: section through nest, A, of _Odynerus reniformis_; B, of _Eumenes arbustorum_. _a_, The suspended egg of the wasp; _b_, the stored caterpillars. (After André.)] It is known that other species of _Eumenes_ construct vase-like nests; _E. unguiculata_, however, according to an imperfect account given by Perris, makes with earth a closed nest of irregular shape, containing three cells in one mass. The saliva of these builders has the power of acting as a cement, and of forming with the clay a very impenetrable material. One species, _E. coarctata_, L. of this genus occurs in Britain. The clay {74}nests (Fig. 29) of this Insect are often attached to the twigs of shrubs, while those of the two species previously mentioned are usually placed on objects that offer a large surface for fixing the foundations to, such as walls. According to Goureau the larva of this species forms in one corner of its little abode, separated by a partition, a sort of dust-heap in which it accumulates the various débris resulting from the consumption of its stores. _Eumenes conica_, according to Horne, constructs in Hindostan clay-nests with very delicate walls. This species provisions its nest with ten or twelve green caterpillars; on one occasion this observer took from one cell eight green caterpillars and one black. It is much attacked by parasites owing, it is thought, to the delicacy of the walls of the cells, which are easily pierced; from one group of five cells two specimens only of the _Eumenes_ were reared. [Illustration: Fig. 29—Nest of _Eumenes coarctata_: A, the nest attached to wood; B, detached, showing the larva. _a_, the larva; _b_, the partition of the cell. (After André.)] _Odynerus_, with numerous sub-genera, the names of which are often used as those of distinct genera, includes the larger part of the solitary wasps; it is very widely distributed over the earth, and is represented by many peculiar species even in the isolated Archipelago of Hawaii; in Britain we have about fifteen species of the genus. The _Odynerus_ are less accomplished architects than the species of _Eumenes_, and usually play the more humble parts of adapters and repairers; they live either in holes in walls, or in posts or other woodwork, or in burrows in the earth, or in stems of plants. Several species of the sub-genus _Hoplopus_ have the remarkable habit of constructing burrows in sandy ground, and forming at their entry a curvate, freely projecting tube placed at right angles to the main burrow, and formed of the grains of sand brought out by the Insect during excavation and cemented together. The habits of one such species were described by Réaumur, of another by Dufour; and recently Fabre has added to the accounts of these naturalists some important information drawn from his own observations on _O. reniformis_. {75}[Illustration: Fig. 30.—_Odynerus antilope_ ♀. Britain.]