14 BULLETIN 1222, U. S. DEPARTMENT OF AGRICULTURE. 
le 
In larvae of the flies Sarcophaga and Lucilia, Herms (#), usin 
the percentage increment method of Minot (5), found that "th 
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 from 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- 
