12 



BULLETIN 1222, U. S. DEPARTMENT OF AGRICULTURE. 



as dearth of nectar, while the food consisting mainly of honey and 

 pollen, such as is fed to the older larvae, could be affected by such 



circumstances, as the 

 data given suggest. 



TIME OF CHANGE IN COMPO- 

 SITION OF BROOD FOOD. 



It has been shown by 

 the investigations of 

 von Planta (7) (Table 

 4), that the younger 

 larvae receive a food 

 that is much richer in 

 fat and albuminous 

 constituents than that 

 given the older larvae. 

 In the case of the older 

 worker larva? this food 

 is discontinued and a 

 food consisting of a 

 mixture of nectar (or 

 honey) and pollen is 

 substituted. The latter 

 food was shown to be 

 much higher in sugar 

 content, while the fat 

 and albuminous con- 

 tent decreases consid- 

 erably. This food also 

 contains undigested 

 pollen grains, which 

 are absent in the food 

 of the younger larvae. 

 Von Planta stated that 

 this change in the com- 

 position of the food oc- 

 curs when the larva is 

 4 days old. From the 

 observations of the 

 writers, as well as of 

 others, however, this 

 change is found to take 

 place as early as dur- 

 ing the third day. This 

 was demonstrated by 

 the fact that through- 

 out these experiments 

 undigested pollen 

 grains were regularly 

 found in the food of larvae no more than 3 days old from the time of 

 hatching from the egg, often in sufficient amounts to color the food 

 slightly. Also, as mentioned above, the coincidence of the curves in 

 Figure 2 for rates of growth up through the third day even under 



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Fig. 3. — Weight of unconsumed food in the cell in re- 

 lation to weight of honeybee larva, (Table 3.) 



