These nests (Figs. [340] and [341]) are filled with cells of oblong form arranged irregularly. At first sight they might be taken for little lumps of earth plastered against the wall. When the perfect insect emerges, it is obliged to soften the mortar with its saliva, and to remove it, grain by grain, with its mandibles. The nests of Chalicodomas are common in the environs of Paris, on walls of rough stones exposed to the south. They are often to be found in the parks of Meudon, of Conflans, of Vésinet, &c.
The Leaf-cutting Bees (Megachile) are not less worthy of remark in their habits. These insects make their nests in tubes lined with the leaves of the rose, the willow, the lilac, &c., placed in a cylindrical burrow. Each nest contains generally from three to six cells, separated by partitions of leaves. They cut off the pieces of leaves they require with their mandibles, the notches being wonderfully cleanly cut, as if they had been done with a punch.
Fig. 343.
Gallery of an Andrena.
They make as many as eight or ten envelopes in succession with the leaves, which, as they get dry, contract, keeping, however, the form given to them by the insect. The cells destined to receive the eggs acquire thus a certain solidity. [Fig. 342] represents the nest of the Megachile.
The Upholsterer Bees (Anthocopas) line their nests with the petals of flowers, as, for example (Papaver rhæas), the corn-poppy. Their burrows are made perpendicularly in the beaten earth of roads, and each contains one solitary cell, lined with portions of petals. When the egg has been laid at the bottom of this cell, the bee fills up the rest of the hole with earth, to hide it from notice.
The Mining Bees (Andrenæ) hollow out in the ground tubular galleries ([Fig. 343]). They are not larger than ordinary flies. A great number of other bees are known, but their habits are little understood, and we shall not occupy ourselves about them.
Wasps.