The great majority of the species of short-tongued bees found in Britain belong to the genera _Andrena_ and _Halictus_, and with some others constitute the Andrenides of many writers. _Halictus_ includes our smallest British bees. Their economy escaped the earlier observers, but has recently been to some extent unravelled by Smith, Fabre, Nicolas, Verhoeff, and others, and proves to be {24}of great interest and variety. Fabre observed _H. lineolatus_ and _H. sexcinctus_[23] under circumstances that enabled him to give them continuous attention, whenever requisite, throughout a whole year. These bees are to a certain extent social; they are gregarious; each bee works for its own progeny, but there is collaboration between members of a colony, inasmuch as a piece of general work is undertaken from which more families than one derive benefit. This common work is a gallery, that, ramifying in the earth, gives access to various groups of cells, each group the production of a single _Halictus_; in this way one entrance and one corridor serve for several distinct dwellings. The work of excavation is carried on at night. The cells are oval, and are covered on the interior with a delicate waterproof varnish; Fabre considers this to be a product of the salivary glands, like the membrane we noticed when speaking of _Colletes_. In the south of France both sexes of these species are produced from the nests in September, and then the males are much more numerous than the females; when the cold weather sets in the males die, but the females continue to live on in the cells underground. In the following spring the females come out and recommence working at the burrows, and also provision the cells for the young; the new generation, consisting entirely of females, appears in July, and from these there proceeds a parthenogenetic generation, which assumes the perfect form in September, and consists, as we have above remarked, in greater part of males. Pérez,[24] however, considers that Fabre's observations as to the parthenogenetic generation were incomplete, and that males might have been found a little earlier, and he consequently rejects altogether the occurrence of parthenogenesis in _Halictus_. Nicolas confirms Fabre's observations, so far as the interesting point of the work done for common benefit is concerned; and adds that the common corridor being too narrow to permit of two bees passing, there is a dilatation or vestibule near the entrance that facilitates passage, and also that a sentinel is stationed at this point.