190 HOW TO KEEP BEES 



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 pro- 

 visional. 



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 pro- 

 duced 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 har- 

 vested 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 



