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



surrounded by food. All seemed large as measured by the eyepiece 

 micrometer. One unhatched egg was seen. According to previous 

 observations of the writer, these eggs should have hatched between 

 11.15 a. m. and 1.15 p. m. on this date. On July 26, 5 of the 13 

 larvae present were weighed, the individual weights in milligrams 

 being as followed : 5.05, 6.1, 20.9, 23.4, 28.9. Considerable differ- 

 ences in the size of the larva? were evident on examination of the 

 comb. Three of the. larvae covered an area of less than one-half of 

 the diameter of the bottoms of their respective cells, but most of 

 them nearly or quite filled the bottoms of the cells. All of the larvse 

 were supplied with an excess of larval food. 



VARIATIONS IN RATE OF GROWTH. 



An outstanding feature of these observations is the great individ- 

 ual variation in the daily rate of growth as manifested in the dif- 

 ferences between the weights of the 5 to 10 larvse of the same age 

 in different lots, as well as in the differences between individuals of 

 the same age in the same lot. These considerable differences natur- 

 ally led to the suspicion that they might have been due to the method 

 used in selecting newly hatched larvae. The experiment described 

 under Lot 7 was intended to test this supposition. As already 

 stated, larvae 3 days old, hatched from eggs laid within a determined 

 3-hour period, showed wide divergences in individual weight. 

 There were on hand two series of larvae, each from a single batch -of 

 eggs laid within a known period of 2 hours, preserved in alcohol. 

 The greater part of these were fixed in their cells, the earlier stages 

 being embedded in the coagulated larval food and therefore unsuit- 

 able for weighing. Five larvae 3 days old of one lot were free from 

 foreign material and suitable for weighing for comparison with one 

 another. These showed on superficial examination considerable dif- 

 ferences in size. These larvae were weighed separately, the weights 

 in milligrams being as follows: 5.7, 7.35, 7.5, 9.8, 10.4. Although 

 the differences in weight between the different individuals of this 

 lot are not as great as between those of most of the other lots, still 

 they are considerable, the difference between the smallest and the 

 largest amounting to nearly 100 per cent. This, result, taken in con- 

 junction with the great differences between larvae of the same age 

 in different lots, makes it reasonable to conclude that considerable 

 differences exist in the rate of growth of bee larvae. 



In fly larvae Herms (£) determined that "there is an optimum 

 when enough nourishment has been taken to pass through the 

 metamorphosis to the best advantage." This optimum is evidently 

 represented in the honeybee by a weight of about 158.31 milligrams 

 when the larvae are sealed by the worker bees. As far as the pre- 

 ceding observations on the honeybee are concerned, the optimum 

 weight virtually coincides with the average weight at maturity. 



LENGTH OF THE LARVAL PERIOD. 



As the data show, sealing may begin as early as the end of the 

 fourth day after hatching (Lots 2 and 3) and as late as the middle of 

 the fifth day (Lots 1 and 5), the average for the five lots being about 

 4f days (Table 1-). It is noteworthy that a difference of half a day 

 may exist between two lots from the same hive, not only during 



