160 



Journal of Agricultural Research voi. xxvm, No. 2 



much earlier than stated by Von Planta (35, 26). The young larvae receive a 

 food rich in nitrogenous material and relatively low in sugar and in which pollen 

 grains are absent during about the first two and a half days of larval Ufe. A 

 large part of this, which is several times in excess of the weight of the larva 

 during the first 24 hours or more {SB) (Table VIII), seems to be placed in the 

 ceU with the newly hatched larva at one time soon after hatching, which justifies 

 the assumption of mass feeding. During this period, assimilation must be very 

 rapid, because the greatest relative growth occurs during the first two to three 

 days (Table VIII) and also because no unassimilated sugar can be demonstrated 

 in the larva during this period, even though the food contains about 5 per cent 

 reducing sugar (Table V) . The high nitrogenous content of the food apparently 

 serves for rapid cell building, while the sugar is largely consumed in producing 

 energy for this rapid growth; little storage of glycogen or fat occurs during this 

 period. The nature and composition, as well as the biochemical reactions of 

 this early food, as described by Koehler {26) , suggest that it is a glandular secre- 

 tion rather than a regurgitation of predigested honey and poUen from the ven- 

 triculus. The chances of larvae of this age during mass feeding receiving infective 

 material are, therefore, slight. 



Table VIII. — Ratio of weight in milligrams of unconsumed food in cell to weight 

 of larva at different approximate ages {from Sturtevant {SB)) 



" From Nelson {SS), 



Soon after the second day, a change in the composition of the food of the larva 

 occurs, accompanied by a change in the method of feeding it by the nurse bees 

 {26) . The larva is now fed at approximately the rate at which the food is ingested 

 by it, the demand for food rapidly increasing, accompanied by the great increase 

 in actual body weight, until the time of sealing. The food now contains many 

 entire pollen grains and has a much higher sugar content, nearly 14 per cent, 

 and a relatively lower nitrogenous content (Table III). The principal ingredi- 

 ents are now honey or nectar and pollen. It is well known that honey which is 

 gathered while disease is present in the hive usually carries infection. There is, 

 therefore, a much greater opportunity for infection to occur when the larvae are 

 being given a food containing unmodified honey as one of its chief ingredients. 

 Furthermore, the constant care of the larvae during the period of progressive 

 feeding and the large number of nurse bees which visit the cell still further increase 

 the chances of infection being introduced during the period of progressive feeding. 

 It is the young bees in the colony which act as nurses, and these bees are also the 

 ones which clean the hive, so that they are more apt to have infected material 

 on their mouth parts and elsewhere than are old field workers. There can, 

 therefore, be little doubt that it is almost exclusively during the period of pro- 

 gressive feeding that infection normally occurs. Under normal feeding condi- 

 tions the disease organisms can not develop in the larval intestine until after 



