NOR DUE TO THE USE OF A PASSWORD. 151 
There was no dead ant either in the nest or the outer 
box. 
Lastly, on October 15, I put in four more at 7 a.M., 
and watched them all day at short intervals. They 
exhibited no sign of fear, and were never attacked. 
In fact, they made themselves quite at home, and were 
evidently, like the preceding, recognised as friends. For 
the sake of comparison at noon I again put in a stranger. 
Her behaviour was in marked contrast. The preceding 
ants seemed quite at home, walked about peaceably 
among the other ants, and made no attempt to leave 
the nest. The stranger, on the contrary, ran uneasily 
about, started away from any ant she met, and made 
every effort-to get out of the nest. After she had 
three times escaped from the nest, I put her back with 
her own friends. 
Thus, then, when a nest of Formica fusca was 
divided early in spring, and when there were no young, 
the ants produced in each half were in twenty-eight 
cases all received as friends. In no case was there the 
slightest trace of enmity. 
These observations seem to me conclusive as far as 
they go, and they are very surprising. In the previous 
experiments, though the results were similar, still the 
ants experimented with had been brought up in the 
nest, and were only removed after they had become 
pupe. It might therefore be argued that the ants 
having nursed them as larve, recognized them when 
they came to maturity; and though this would cer- 
