The most interesting part of their history is perhaps that upon which I have not yet enlarged, namely, the structure of their nests. This is particularly the case with the carder-bees, which felt and plait the filaments of moss to form its whole enclosure. Such species select a spot close to an abundant supply of the material; this they bite off and form pellets of. To these nests a moderately long arched passage is formed of the same material, of sufficient size to permit the free passage of the bees to and fro. This necessarily is shorter at first and leads to a smaller receptacle when the parent bee works alone. But as her offspring of workers increases, the passage is lengthened and the nest enlarged. To construct it, when in full activity, the bees form a chain, one behind the other, extending from the growing material to the entrance of their passage to the nest, all their heads being turned towards the moss and their backs to the nest. The first bites off the raw material, rolls it and twists it, and passes it to the second, by whom and the succeeding ones it undergoes further manipulation, and where the chain terminates at the commencement of the passage another bee receives it and conveys it along this into the interior, and then applies it itself or passes it to others thus employed where it is required. A vaulted covering and sides is thus formed or extended within the cavity by the plaiting or wreathing together of these sprigs of moss, and the inside of which is further strengthened by being plastered with a coating of the pseudo-wax, which, however, smells much like true wax, and with which the lower loose filaments of the moss are intermingled, that one cannot be separated from the other without tearing the whole to pieces. Thus ingeniously do these insects enclose their home. These nests are not always on the surface, but often cavities of the necessary size are thus lined, and then they are doubly secure. Within these nests, with the increase of the population the number of the cocoons of course increases, as they are never used twice over, excepting that when they are conveniently situated for the purpose they are converted into honey pots. Thus sometimes several layers are formed of these irregularly-placed cocoons, of which the longest diameter is, however, always perpendicular to the horizon. In this way _B. muscorum_, _senilis_, _fragrans_, and others build. Some use a naked cavity, and merely secure it in its crevices from the filtering intrusion of rain or other water, the closing patches being formed of the usual waxy material. This is the practice of _B. terrestris_, which associates the largest communities of all; and _B. lapidarius_ seeks cavities among stones or in the earth, and forms a nest of a regular oval, but merely clothes the sides, which is done by bits of moss and grass carried carefully home. The domestic arrangements within are much the same in all, the prolific females and the neuters being the labourers, which perform all the duties of building, the collecting and caring for the young, the function of the males being limited to the perpetuation of the species.