_Some of the hairs of the body plumose; parts of the mouth elongated, sometimes to a great extent, so as to form a protrusible apparatus, usually tubular with a very flexible tip. Basal joint of hind foot elongate. No wingless adult forms; in some cases societies are formed, and then barren females called workers exist in great numbers, and carry on the industrial operations of the community. Food always derived from the vegetable kingdom, or from other Bees._ There are about 150 genera and 1500 species of bees at present known. Some call the division Mellifera instead of Anthophila. The term Apidae is used by some authorities to denote all the bees, while others limit this term to one of the families {11}or sub-divisions. The bees are, as a rule, distinguished from other Hymenoptera by the hairs, by the great development of the mouth parts to form a proboscis (usually, but not correctly, called tongue), and by the modification of the hind-legs; but these distinctive characters are in some of the species exhibited in so minor a degree of perfection that it is not easy to recognise these primitive forms as Anthophila. A few general remarks on the three points mentioned will enable the student to better appreciate the importance of certain points we shall subsequently deal with. [Illustration: Fig. 5—Hairs of Bees: A, simple hair from abdomen of _Osmia_; B, spiral hair from abdomen of _Megachile_; C, plumose hair from thorax of _Megachile_; D, from thorax of _Andrena dorsata_; E, from thorax of _Prosopis_.] The bees are, as a rule, much more covered with hair than any other of the Hymenoptera. Saunders[10] states that he has examined the structure of the hairs in all the genera of British Aculeata, and that in none but the Anthophila do branched and plumose hairs occur. The function of this kind of hairs is unknown; Saunders suggests[10] that they may be instrumental in the gathering of pollen, but they occur in the parasitic bees as well as in the males, neither of which gather pollen. The variety of the positions they occupy on the body seems to offer but little support to the suggestion. Not all the hairs of the bee's body are plumose, some are simple, as shown in Fig. 5, A, and this is specially the case with the hairs that are placed at the edges of the dilated plates for carrying pollen. In some forms there is an extensive system of simple hairs all over the body, and the "feathers" are distributed between these; and we do not see any reason for assuming that the feathered are superior to the simple hairs for gathering and carrying pollen. Some bees, _e.g._ _Prosopis_, _Ceratina_, have very little hair on the body, but nevertheless some plumose hairs are always present even though they be very short.