148 Beekeeping 



While bees can convert sucrose (cane sugar) into levulose 

 and dextrose and can digest maltose, they cannot digest 

 certain other sugars. There is also considerable evidence 

 that dextrine cannot be digested and that the presence in 

 the food of unusual amounts of dextrine may produce the 

 condition known as dysentery. It has also been found 

 that certain proteids which have been used as substitutes 

 for pollen cannot be digested. The alimentary canal of 

 the bee, therefore, appears to be a highly specialized system, 

 incapable of any considerable flexibility. Bees would evi- 

 dently fail to be nourished by the mixed diets of many 

 other species, which is additional argument against at- 

 tempted homologies with human digestion. 



CIRCULATION 



When the products of digestion are absorbed and traverse 

 the alimentary canal wall, they must be carried to the 

 various tissues for assimilation. This is done by means 

 of the blood. In the higher animals blood is normally 

 confined in blood vessels which carry it throughout the 

 body, but in the bee, as in other insects, the blood bathes 

 the various organs, filling up the interstices between them. 

 These spaces may, however, be so arranged that the blood 

 flows in definite channels or sinuses. The blood is further 

 confined to definite paths by membranes stretched across 

 the dorsal and ventral walls of the abdomen {DDph and 

 VDph, Fig. 78) which bound the chief sinuses. These 

 diaphragms have a rhythmical motion and assist in the 

 circulation of the blood. The heart (Ht) is located dorsal 

 to the dorsal diaphragm, this sinus being therefore known 

 as the pericardial chamber. The heart is a long muscular 

 tube consisting of four chambers lying in the third, fourth, 

 fifth and sixth segments of the abdomen. In each of these 

 segments is a valvular opening (ostium, Ost) on each side 

 for the admission of blood from the pericardial chamber, 

 and there are also segmental valves to prevent a backward 



