8 BULLETIN 1222, U. S. DEPARTMENT OF AGRICULTURE. 



grooves one-fourth of an inch in diameter in the surface of a flat 

 block of wood which had been impregnated with melted wax. These 

 cells were closed at the ends with wax and at the top with cover slips. 

 The larvae were then placed in an incubator and kept at 37.5° C. All 

 of these larvse spun more or less perfect cocoons, but only two suc- 

 ceeded in forming normal pupa?. From these two pupae perfect adult 

 bees emerged. The weight of these in milligrams, as compared with 

 their larvae and the weights of normal larvse and pupae, are given 

 below : 



Larva. Adult. 



No. 1 115.0 68.1 



No. 2 144. 1 94. 2 



Normal 158. 3 112. 



Since adult bees from fully fed larvae reared under similar artificial 

 conditions are only slightly under normal weight, it is possible to 

 produce undersized bees from larvae that are not fully fed. Under- 

 sized or dwarf bees are familiar to most beekeepers, but whether 

 they are due to underfeeding of the larvae is not definitely known. 



METHODS, LOT 8. 



In order to counteract variations observed in the earlier experi- 

 ments as much as possible, an attempt was made during the work of 

 1922 to perfect the method suggested under Lot 7, which seemed to 

 give promise of the best results. A space in the middle of a hive wide 

 enough for two brood frames was partitioned off with queen-excluding 

 zinc at either side and at the entrance. This was to prevent the queen 

 from escaping in any way after the cover was placed on the hive, but 

 the workers could come and go at will. A fairly strong colony of bees 

 was transferred to this hive, placing one frame nearly filled with 

 brood in this partitioned-off space, with a second frame either empty 

 or with only a small amount of sealed brood in it. The queen was 

 then confined in this chamber. The nearness of the well-filled brood 

 comb to the empty comb generally induced the queen to lay a fairly 

 large number of eggs in a period of 12 hours or less. 



To obtain average live weights of larvae of known age at definite 

 age periods frames of eggs were removed from this chamber after 

 a definite length of time. The frame removed was replaced by 

 another empty one for the next series. The removed frame of eggs 

 then was kept with several other frames of brood covered with nurse 

 bees in a super over a strong colony, with the queen confined below 

 by a queen excluder. After 3 days' incubation as eggs, at intervals 

 of 24 hours each, larvae were removed by means of small forceps for 

 weighing. So far as possible, the time of day selected for weigh- 

 ing the larvae corresponded to the middle of the egg-laying period 

 for that series. A method of weighing similar to that previously 

 employed was used, except that, to reduce the probable error, five 

 larvae were taken for each weighing instead of individual larvae. 

 Larvae of average maximum size for the age period, and as nearly 

 alike in size as possible when selecting from gross appearances, were 

 chosen for each group of five. These were carefully removed, 

 cleaned of food material, placed in a watch crystal, and weighed 

 immediately by means of a chemical balance. Even with this 

 method more or less variation in weight for each age period was 



