2 BULLETIN 1222, U. 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 T915 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 larva? 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 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. 



