16 



BULLETIN 1222, U. S, DEPARTMENT OF AGRICULTURE. 



CORRELATION WITH TIME SPENT IN NURSING. 



The effect of these food requirements upon the amount of work 

 necessary to be done by the nurse bees in relation to the rate of 

 growth of the larvae and nature of the food is well illustrated by 

 the observations of Lineburg in Part II of this bulletin. He founcl 

 that in the time spent by nurse bees in caring for larvae there is prac- 

 tically 100 per cent increase on the first day over that at the time of 

 hatching from the egg. Food is never placed in the cell until soon 

 after the larva hatches. On the second day this again decreases 

 about an equal amount, but begins to increase again to a remarkable 

 degree, particularly after the third day. From the third day on 



the living weight (fig. 2) and the 

 time spent in feeding (fig. 13) show 

 a remarkable correlation. The high 

 point for feeding on the first day 

 corresponds with the maximum ex- 

 cess of unconsumed food in the cells 

 at this time. It seems probable that 

 the nurse bees place an excess of the 

 predigested food in the cell soon 

 after the egg hatches, sufficient for 

 the larva for about two days, so that 

 only a minimum of attention is re- 

 quired until the change in the com- 

 position of the food takes place, at 

 which time increasingly greater de- 

 mands are made by the larva for 

 honey and pollen. 



Since the greatest relative increase 

 in growth takes place during the 

 period of uniform, highly nitrogen- 

 ous food and the greatest storage 

 of reserve energy-producing mate- 

 rials occurs after the food has 

 changed in composition it may be 

 assumed from the observations cited 

 that any variations in honey-flow will affect the rate of growth of 

 the older larvae more than the younger larvae. 



GENERAL APPEARANCE OF LARVAE OF DIFFERENT AGES. 



The general appearance of larvae of different ages, particularly 

 with reference to their size and position in the cell, provides criteria 

 by which to judge the age of the brood. 



The newly hatched larva (fig. 6) has a total length of 1.6 milli- 

 meters. It is usually bent in a curve approximating a semicircle and 

 lies on its side on the bottom of the cell. At this stage it is slender 

 as compared with the later stages, tapers gradually from the head, 

 and is nearly transparent. It usually lies near the center of the base 

 of the cell in a mass of transparent larval food which does not exceed 

 in diameter one-half that of the base of the cell. A circle drawn 

 around the larva in its usual flexed position would closely approxi- 

 mate 1 millimeter in diameter (fig. 1). A larva may lie on either 



Fig. 6. — Larva of honeybee newly 

 hatched from the egg. 

 Figures 6 to 11 were all drawn 

 with the aid of the camera lucida 

 from material preserved in alcohol. 

 A special effort was made to secure 

 as far as possible specimens repre- 

 sentative of the average size of 

 larvae of the age designated. In 

 figures 6 to 10, inclusive, the larva? 

 are represented as seen from the 

 mouth of the cell, the outlines of the 

 latter being represented by a hexa- 

 gon and drawn accurately to scale. 



