AFTER SEPARATION FOR NEARLY TWO YEARS. 123 
attacked, as if some of the ants, perhaps the young ones, 
did not recognise them. Still they were never killed, 
or driven out of the nest, so that evidently when a 
mistake was made, it was soon recognised. No one 
who saw the different manner in which these ants and 
strangers were treated, could have the slightest doubt 
that the former were recognised as friends and the 
latter as enemies. The last three were put back on 
May 14, 1877, that is to say, after a separation of a 
year and nine months, and yet they were amicably re- 
ceived, and evidently recognised as friends ! 
These observations were all made on Formica fusca, 
and it is of course possible that other species would 
behave in a different manner. 
Indeed, in this respect Lasiws flavus offers a sur- 
prising contrast to F. fusca. I was anxious to see 
whether the colonies of this species, which are very 
numerous round my house, were in friendly relations 
with one another. With this view, I kept a nest of L. 
flavus for a day or two without food, and then gave 
them some honey, to which they soon found their way 
in numbers. I then put in the midst of them an ant 
of the same species from a neighbouring nest; the 
others did not attack, but, on the contrary, cleaned her 
—though, from the attention she excited and the 
numerous communications which took place between 
her and them, I am satisfied that they knew she was 
not one of themselves. After a few minutes she accom- 
panied some of the returning ants to the nest. They 
