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



In larvae of the flies Sarcophaga and Lucilia, Herms (2), using 

 the percentage increment method of Minot (5), found that "the 

 tendency is for growth to decrease in rate uniformly." This rule 

 does not apply to the honeybee, however, as the averages and percen- 

 tage increases of all lots show (Tables 1 and 2) . Moreover, the aver- 

 age per cent in each lot tends to reach a maximum at the end of the 

 second day, with the exception of Lot 2 (Table 1). The individuals 

 of this lot are open to the suspicion of being actually older than 

 estimated. This suspicion, if confirmed, would explain the circum- 

 stance of the maximum per cent increment falling at the end of the 

 first instead of at the end of the second day. After the second day 

 the average percentage increment of the five lots combined shows a 

 steady drop until maturity. 



CORRELATION OF FOOD WITH THE RATE OF GROWTH. 



Physiologically food may be defined as any substance taken in 

 by an organism and made use of for any purpose. Nitrogenous 

 material is necessary for growth and repair of tissues, no large 

 amount being stored, except as tissue or protoplasmic substance. 

 Sugars and fats are readily assimilated and stored in the tissues 

 as glycogen and neutral fats and are sources of energy by oxidation 

 for various purposes. 



It is seen troni Figure 5 that the greatest per cent of daily increase 

 in growth for the honeybee larva takes place during the first three 

 days of larval life, with the maximum at two days. After three days 

 the per cent of daily increase is noticeably less, although the actual 

 increase in weight of the larva rises rapidly to the maximum just 

 after sealing has taken place. According to results of the analyses 

 by Straus, when, during the first three days, the nitrogenous con- 

 tent of the food is high for the purpose of tissue building, rela- 

 tively little storage of glycogen or fat takes place. Since little 

 energy is required for the slight movements made by the larva, after 

 the change in the composition of the food takes place and it becomes 

 predominantly carbohydrate (that is, high in sugar content from 

 the honey used), the great storage of glycogen takes place which is 

 to serve as a source of energy during metamorphosis. This again 

 seems to divide the larval period at about the 3-day age. 



Again, as may be observed from the data given in Table 3 (figs. 

 3 and 4), at the time when the greatest relative increase in weight 

 occurs and the food has the highest growth-producing, nitrogenous 

 content, there is a marked excess of unconsumed food in the cells 

 nearly four times the weight of the larva 1 day old. It will be noted 

 that the weight of the 1-day-old larva (0.65 milligram) plus the 

 weight of the food unconsumed in the cell on the first day ( 3.96 milli- 

 grams) practically equals the weight of the larva on the second 

 day (4.745 milligrams) (Table 2). This relation does not continue, 

 because the excess of food decreases, and the change in composition 

 occurs soon afterwards. After the third day the larva has developed 

 to a size sufficient to consume an increasingly larger volume of food as 

 soon as it is placed in the cell, particularly as probably considerable 

 food is actually placed directly in the mouth of the larva. This ac- 

 counts for the small amount or almost total absence of food in the cells 

 for the late stages just prior to sealing. There is a slight increase 

 in weight, however, after sealing takes place. Therefore, correspond- 



