Fig. 4, 3) are situated in the thorax; their outlets unite into a common duct, which joins the ducts from the postcerebral glands, the two systems of glands opening through a common opening.
The mandibulary glands or system IV. are two small glands one on each side opening at the base of the mandible.
There has been much discussion regarding the function of these different glands; and even now any statement of conclusions must be regarded as provisional.
The supracerebral glands are large in nurse bees and shrunken in the old bees that no longer nurse the brood; they are normally found only in the workers. It is therefore believed that they secrete the milky food, commonly called royal jelly, which is fed to all larvse during the first days of their development, to the queen larvae throughout their development, and to the adult queen during the egg-laying period. The food fed worker and drone larvae during the latter part of their development is produced in the chyle-stomach of the nurse bees, and is semi-digested food.
The other systems of glands enumerated above produce the saliva, which is supposed to perform a great variety of functions. "It helps the digestion; it changes the chemical condition of the nectar harvested from the flowers; it helps to knead the scales of wax of which the combs are built, and perhaps the propolis with which the hives are varnished. It is used also to dilute the honey when too thick, to
