1940] 
Caste Determination in Ants 
109 
male, and of the 83, 51 are predetermined as queens and 32 
predetermined as workers, then the chances of obtaining 1 9 
workers, 32 queens (colony A: 78%) plus 23 workers, 19 
queens (colony B: 45%) are less than 1:100 the chances of 
obtaining an equal division of 16 workers, 25-26 queens in 
each colony. Unfortunately, I will be unable to undertake 
corroborative experiments which should be performed before 
these results may be considered conclusive. 
Days 
Fig, 1. Number of larvae pupated at a given time plotted against days 
after beginning of experiment. A, colony A; B, colony B. Solid lines, 
pupation curves of total brood ; broken line, pupation curve of queens 
alone of colony B. It may be noted that in B, workers and males did 
not start pupating until the 13th day, or one day before all the queen 
larvae had finished pupating. 
The two colonies responded very differently in the rate 
of maturation of the larvae. From figure 1, it will be noted 
that during the period when the entire brood of colony A 
is pupating, the queen larvae alone, for the most part, are 
pupating in colony B. Even though the latter colony is get- 
ting much less food, the queen larvae have matured at the 
same time as the larvae in the well-fed colony, while the 
maturation time for the rest of the brood lags considerably 
behind that of the queen larvae. 
Conclusions. 
It may be affirmed that, in all probability, with the ant 
Leptothorax curvispinosus only one type of female egg is 
