12 
BULLETIN 1222, U. S. DEPARTMENT OF AGRICULTURE. 
./^O 
/oo 
J>0 
TO 
eo 
as dearth of nectar, while the food consisting mainly of honey and 
pollen, such as is fed to the older larvae, could be affected by such 
circumstances, as the 
data given suggest. 
TIME OF CHANGE IN COMPO- 
SITION OF BROOD FOOD. 
It has been shown by 
the investigations of 
von Planta {7) (Table 
4), that the younger 
larvae receive a food 
that is much richer in 
fat and albuminous 
constituents than that 
given the older larvae. 
In the case of the older 
worker larvae this food 
is discontinued and a 
food consisting of a 
mixture of nectar (or 
honey) and pollen is 
substituted. The latter 
food was shown to be 
much higher in sugar 
content, while the fat 
and albuminous con- 
tent decreases consid- 
erably. This food also 
contains undigested 
pollen grains, which 
are absent in the food 
of the younger larvae. 
Von Planta stated that 
this change in the com- 
position of the food oc- 
curs when the larva is 
4 days old. From the 
observations of the 
writers, as well as of 
others, however, this 
change is found to take 
place as early as dur- 
ing the third day. This 
Avas demonstrated by 
the fact that through- 
out these experiments 
undigested pollen 
grains were regularly 
found in the food of larvae no more than 3 days old from the time of 
hatching from the egg, often in sufficient amounts to color the food 
slightly. Also, as mentioned above, the coincidence of the curves in 
Figure 2 for rates of growth up through the third day even under 
+o 
JO 
20 
/o 
WCO//SVA) 
€P F000 { 
/*> 
L'\ 
7 ^ 
f \ 
^9&£ //V £>s?y^ 
Fig. :j. — Weight of unconsumed food in the cell in 
lation to weight of honeybee larva, (Table 3.) 
