122 LIFE : OUTLINES OF GENERAL BIOLOGY 



t\'pes. And the non-militant members, workers in the more literal 

 sense, have diverse functions to fulfil. There are the foragers who cut 

 off segments of leaf from the trees and carry them back to the 

 underground city. Another function is the chewing of the leaves 

 into a green paste, on which is grown a fungus, the sole food beneath 

 the ground. A third function is looking after the young stages. The 

 variety of function among non-reproductive ants is often associated 

 with polymorphism of structure. Wheeler points out that they can 

 be arranged in a graduated series, beginning with large and huge- 

 headed individuals, more like the queen in stature, and ending 

 with minute small-headed individuals, which may be almost like 

 dwarf species. In Carebara, for instance, the worker may be a 

 thousand times smaller than the queen! The largest of the worker 

 tN'jX's may stTve as soldiers or policemen, yet their powerful jaws 

 may have a pacific function- — primarily, secondarily, or both, who 

 shall say— for they may be used to crack seeds and hard parts of 

 insects, "so that the softer parts may be exposed and eaten by the 

 smaller individuals". These may be foragers, nurses, cultivators, 

 sappers and miners, and so forth. Now it happens in some species 

 that only the maxima? (the soldiers) and the minima? (the ordinary 

 workers) are left, the intermediate grades being eliminated. "In 

 still other genera, where soldiers were not needed, or were too expen- 

 sive to rear and maintain, on account of their great size and appetites, 

 they too have been eliminated and the worker caste is represented 

 only by the tiniest individuals of the originally polymorphic series." 



Very quaint is the picture Bates gave in his Naturalist on the 

 Aviazons of the Saiiba or L'mbrella Ant of Brazil. The hard destruc- 

 tive work of cutting discs from the leaves of certain trees is done by 

 workers with relatively small heads. Others, called "worker-majors", 

 with huge heads, walk about looking on, without very obvious 

 functions. They are not aggressive soldiers, and the foragers do not 

 require foremen. "I think". Bates .says, "that they serve, in some 

 sort, as passive instruments of protection to the real workers. Their 

 enormously large, hard, and indestructible heads may be of use in 

 protecting these against the attacks of insectivorous animals. 

 They would Ix^, on this view, a kind of pieces dc resistance, serving 

 as a foil against onslaughts made on the main body of workers." 

 But there is a third type, represented by very strange fellows, with 

 the same kind of head as the "worker-majors", but "the front is 

 clothed with hairs instead of being poli.shed, and they have in the 

 middle of the forehead a twin simple eye", which none of the others 

 |X)ssess. But these must .serve as instances of the polymorphism and 

 division of lal)our among true ants. 



Among termites (mi.snamed white ants) each non -reproductive 

 caste consists of individuals of both sexes, almost or quite indis- 

 tinguishable externally; and in the great majority of sjx'cies there 



