2 BULLETIN 1222,, IT. S. DEPARTMENT OF AGRICULTURE. 
His paper, however, discusses mainly the results of metabolism in 
relation to age, as determined by chemical analyses of the larvae. 
The observations were made under environmental conditions which 
were probably somewhat different from those found in this country, 
and, although similar, the data can be only relatively comparable to 
those obtained in this country. Part of Straus's data are used in 
Table 2 and Figure 2. 
The following data and observations are presented to clear up 
certain points about which there is need of information and deal 
especially with the rate of growth of the larva, which not only is of 
interest from a scientific point of view but also is of value to the 
breeder of queen bees. Observations concerning some additional 
factors influencing the rate of growth of the larva, as well as in- 
formation concerning the time of change in the composition of the 
larval food, are also given. 
Part of the work herein recorded, referred to under lots 1 to 
7, was done during the years 1915 and 1916 by the senior author. 
This early work was done independently of the work of Straus (9). 
The observations referred to under lot 8 were made mainly during 
August and part of September, 1922, by the junior author inde- 
pendently, and are supplementary to the earlier work. In connec- 
tion with these observations and some made during the same sum- 
mer by Mr. Lineburg, which are described by him in Part II of this 
bulletin, further observations were made on the amount and nature 
of the larval food in relation to the rate of growth. These latter 
were made by the junior author assisted by Mr. Lineburg. 
METHODS, LOTS 1 TO 7. 
Recently hatched larvae were selected by examination, and the 
cells containing them were marked with a quickly-drying paint, 
solutions of anilin stains in alcohol being found good for such tem- 
porary 7 use. The comb containing these larvae was removed at fixed 
intervals, larvae of known ages were removed and weighed in care- 
fully balanced watch crystals, and in case there was any adhering 
larval food this was first washed off and the larva dried. While 
the method of choosing larvae according to their apparent age is 
open to objection, it is believed that errors arising from this source 
are insignificant, especially in the case of larvae chosen from new 
comb, as in the case of lot 1. Toward the close of the experiments 
another method was used which promises to give more accurate 
results. Newly hatched larvae are quite uniform in size and are 
flexed in an arc corresponding roughly to a semicircle having a 
diameter of about 1 millimeter. Eyepiece micrometers were con- 
structed having in the center of each a circle of wire with an inside 
diameter of 1.10 millimeters. The appearance of the newly hatched 
larva with respect to the wire circle is shown in Figure 1. This 
method, when used with a binocular microscope with extensible 
arm, permits an accurate selection of larvae of minimum size. 
OBSERVATIONS, LOTS 1 TO 7. 
WEIGHT OF EGGS. 
On July 10, 1915, 10 eggs about ready to hatch were removed and 
weighed, the total weight being 0.8 milligram, average 0.08 milligram. 
