76 ON THE HABITS OF ANTS. [LECT. 



cinerea, F. fusca, and Lasius niger which lived in my 

 nests for as much as seven years. Of the identity 

 there could be no doubt, because as there was no queen 

 in the nest, no new workers were produced. I also 

 kept two queens of Formica fusca for a still longer 

 period. They were taken in December, 1874, and lived 

 with me till July, 1887, and August, 1888, respectively. 

 They must of course have been born at latest in the 

 spring of 1874, and the elder one must therefore 

 have been nearly fifteen years old at the time of 

 her death. 



The behaviour of ants to one another differs very much, 

 according as they are alone or supported by numerous 

 companions. An ant which would run away in the first 

 case, will fight bravely in the second. 



It is hardly necessary to say that, as a general rule, 

 each species lives by itself. There are, however, some in- 

 teresting exceptions. The little Stenamma Westwoodii 

 is found exclusively in the nests of the much larger F. 

 rufa, and the allied F. pratensis. We do not know 

 what the relations between the two species are. The 

 Stenammas, however, follow the Formicas when they 

 change their nest, running about among them and 

 between their legs, tapping them inquisitively with their 

 antennae, and even sometimes climbing on to their 

 backs, as if for a ride, while the large ants seem to take 

 little notice of them. They almost seem to be the dogs, 

 or perhaps rather cats, of the ants. Another small 

 species, Solenopsis fugax, which makes its chambers 

 and galleries in the walls of the nests of larger species, 

 is the bitter enemy of its hosts. The latter cannot get 

 at the foe, being too large to enter the galleries. The 



