522 NATURAL HISTORY OF ARTHROPODS. 



some of our common small blue butterflies, Lycmna, also are furnisbed with organs for 

 excreting lioney dew", and are attended by ants. 



The relations which exist between different species of ants are in many cases very 

 interesting. On this point I cannot resist quoting again from Lubbock. " It is hardly 

 necessary to say that, as a general rule, each species lives by itself. There are, how- 

 ever, some interesting exceptions. The little Stenomma loesttooodii is found exclu- 

 sively in the nests of the much larger Formica rufa, and the allied F. pratensis. We 

 do not know what the relations between the two species are. The Stenommas, how- 

 ever, follow the Formicas when they change their nests, 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 the 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 host. The latter 

 cannot get at them because they are too large to enter the galleries. The little Solen- 

 opses, therefore, are quite safe, and, as it appears, make incursions into the nurseries 

 of the larger ant, and cai-ry off the larvae as food. It is as if we had small dwarfs, 

 about eighteen inches to two feet long, harboring in the walls of our houses, and every 

 now and then carrying off some of our children into their horrid dens. 



" Most ants, indeed, will carry off the larvae and pupae of others if they get a chance ; 

 and this explains, or, at any rate, throws some light upon that most remarkable pheno- 

 menon, the existence of slavery among ants. If you place a number of larvae and 

 pupae in front of a nest of the horse ant (F. ru/a), for instance, they are soon carried 

 off ; and those which are not immediately required for food remain alive for some 

 time, and are even fed by their captors. 



" Both the horse ant (Formica rufa) and the slave ant (Formica fusca) are abun- 

 dant species, and it must not unfrequently occur that the former, being pressed for 

 food, attack the latter and carry off some of their larvae and pupae. Under these cir- 

 cumstances it no doubt occasionally happens that the pupse come to maturity in the 

 nests of the horse ant, and it is said that nests are sometimes, though rarely, found in 

 which, with the legitimate owners, there are a few F. fuscas. With the horse ant 

 this is, however, a very rare and exceptional phenomenon ; but with an allied species, 

 F. sanguined [a species which occurs both in Europe and America], it has become an 

 established habit. The F. sanguineas make periodical expeditions, attack neighbor- 

 ing nests, and carry off pupaB. When the latter come to maturity they find them- 

 selves in a nest consisting partly of F. sanguineas, partly of their own species, the 

 result of previous expeditions. They adapt themselves to circumstances, assist in the 

 ordinary household duties, and, having no young of their own species, feed and tend 

 those of the F. sanguineas. But though the F. sanguineas are thus aided by their 

 slaves, or, as they should rather, perhaps, be called, their auxiliaries, they have not 

 themselves lost the instinct of working." 



" Polyergus rufescens present a striking lesson of the degrading tendency of sla- 

 very, for these ants have become entirely dependent on their slaves. Even their bodily 

 structure has undergone a change ; the mandibles have lost their teeth, and have 

 become mere nipples, — deadly weapons indeed, but useless except in war. They have 

 lost the greater part of their instincts ; their art, that is, the power of building ; their 

 domestic habits, for they show no care for their own young, all this being done by the 

 slaves; their industry — they take no part in providing the daily supplies; if the 



