There are about 200 different species of solitary bees in northern Europe. Although they may live gregariously, e.g. Colletes daviesanus (see p. 157), they are known as solitary bees because each individual female makes her own nest, lays and tends her eggs and collects her own food.
According to the species, solitary bees may construct their nests in the ground, in plant stems, in timber, or in buildings where crevices in masonry and woodwork offer good shelter. The nests may be built of various types of material, such as mud, plant material, or of substances produced by the bees themselves. The females fill the larval cells with pollen and nectar.