GROWTH AND FEEDING OF HONEYBEE LARVAE. 11 



NATURE AND COMPOSITION OF BROOD FOOD. 



The foregoing observations have a bearing on the much discussed 

 question of the source and nature of brood food at different times 

 during the feeding period. The relation of the composition and 

 amount of brood food to the rate of development may assist in explain- 

 ing the variations observed above. 



To obtain the weight of food unconsumed in the cells, as an indi- 

 cator of the amount of food consumed in relation to the weight of 

 larvae of approximate known age, the following method was used : 



A frame of brood was chosen from a normal colony, containing in 

 an area of 2 or 3 square inches several larvae of uniform size. The age 

 of these larvae was approximately determined by inspection and com- 

 parison in size with the drawings of larvae of definite age (figs. 6 to 

 11). A piece of this comb was then cut out containing about the 

 desired number of larvae. The edges of this piece of comb were 

 trimmed clean with a sharp scalpel and the cells of the comb were cut 

 down so as to reduce the depth of the cells to about half. The edges 

 and all cells containing larvae of abnormal size not desired for weigh- 

 ing were cleaned and dried with swabs of absorbent cotton on the 

 ends of matches. This was clone as rapidly as possible so as to prevent 

 loss by evaporation from the remaining cells. The piece of comb was 

 then carefully weighed. The larvae were then removed with fine 

 forceps, care being taken to remove as little adhering food material 

 as possible, and then the piece was weighed again. The difference 

 between these two weights gives the approximate weight of the larvae 

 (Table 3) . To obtain the weight of the remaining food, each cell was 

 cleaned with a swab of absorbent cotton and the cell was then dried 

 out thoroughly with a second swab to insure complete removal of all 

 the food material. The weight of the empty comb was taken, by 

 which the weight of the food material is determined. The average 

 age of each lot was more approximately determined by comparison 

 and interpolation with the weights of larvae of known age, given in 

 Table 2. 



Unfortunately, owing to lack of time and the small number of de- 

 terminations made, the data given in Table 3 are only approximately 

 accurate. The data are suggestive, however, and considerable inter- 

 esting information may be obtained by correlation with the rate of 

 growth, the time of change in food composition, and the time spent 

 by nurse bees in caring for the larvae of various ages. 



It is noticeable that the small, young larvae are always surrounded 

 by or even are floating on an excessive amount of food material, 

 which has a uniformly grayish-white, pastelike consistency. From 

 the data observed (Table 3, figs. 3 and 4), it was found that up to 

 between the second and third days this excess of food, as indicated 

 by the amount unconsumed in the cell, is considerably greater than 

 the weight of the larva itself. There has been much controversy 

 as to whether the food of the young larva is a secretion from glands 

 or a regurgitation from the ventriculus [Snodgrass (8)1. Its con- 

 sistent lack of pollen grains and uniform appearance suggest secre- 

 tion rather than regurgitation, since if regurgitated it would of 

 necessity contain undigested pollen grains, as these are always found 

 in the ventriculus. If a secretion, the food of the younger larvae 

 would be affected much less by variations in external conditions, such 



