184 LECTURES ON BIOLOGY 



Among ants we find instances comparable to the domesti- 

 cation by man of animals and vegetables. Familiar among these 

 are the fungus-gardens of the notorious leaf-cutting ants of South 

 America, which raid plantations in armies of thousands, cut the 

 leaves into pieces, and carry them to their nests. There the 

 leaves are chewed to a dough which is built up in a loosely- 

 packed heap. In the interior of this the ants form numerous 

 chambers in which they place their young. Soon after this 

 peculiar nest has been formed we are able to observe the appear- 

 ance in the heap of threads of a certain kind of fungus, which 

 form in places little 'heads,' the so-called 'kohlrabi.' These 

 remarkable formations are undoubtedly a cultivation-product of 

 the ants, for if the fungus is withdrawn from the care of the 

 ants the formation of these ' heads ' does not take place. They 

 form the staple food of the ants and are cultivated by them for 

 this purpose. 



The numerous animals which live in the nests of ants and 

 termites have further, as a result of that mode of life, under- 

 gone remarkable changes. In the ' hills ' of termites in the East 

 Indies, South Africa, and the Soudan is found a small species of fly 

 (Termitoxenia), from 1 to 2 millimetres long. If accurate investi- 

 gation had not proved beyond doubt that these little animals are 

 really flies, no one would judge from their appearance that they 

 belong to the Muscidse. In place of the two wings these flies 

 carry small club or hook-like formations which owing to their 

 horny structure are totally unsuitable for flying, and are, in fact, 

 used for very different functions. According to Wasmann, they 

 serve as balancing poles to keep the body in equilibrium. They 

 act further as breathing-tubes, organs of touch, and of exudation 

 which secrete from the blood a volatile substance greatly liked by 

 their hosts. Finally, these transformed wings serve as organs of 

 transport by which they are lifted up by the termites and carried 

 about. These little flies are, in fact, walking contradictions. 

 They are not only diptera without wings, but flies without a 

 larva or pupa stage, and insects without males and females. 

 They are hermaphrodites, both sexes being united in one body. 

 Apart from these flies we know numerous other beetles, etc., 

 which are kept by ants or termites as domesticated animals, fed 

 by their hosts, and have greatly changed in consequence of this 

 altered mode of life. 



