Bibliographical Notices. 398 



about them. Here is an extract from what he says of the Saiiba 

 (CEcodoma cephalotes) : — 



" The workers of this species are of three orders, and vary in size 



from two to seven lines The true working-class of a colony is 



formed by the small-sized order of workers, the worker-minors as 

 they are called. The other two kinds, whose functions, as we shall 

 see, are not yet properly understood, have enormously swollen and 

 massive heads : in one the head is highly polished, in the other it is 

 opake and hairy. The worker-minors vary greatly in size, some 

 being double the bulk of others. The entire body is of very solid 

 consistence, and of a pale reddish-brown colour. The thorax or 

 middle segment is armed with three pairs of sharp spines ; the head 

 also has a pair of similar spines proceeding from the cheeks behind. 



The perfect sexes are winged on their first attaining the adult 



state ; they alone propagate their kind, flying away, previous to the 

 act of reproduction, from the nest in which they have been reared. 

 This winged state of the perfect males and females, and the habit of 

 flying abroad before pairing, are very important points in the economy 

 of ants ; for they are thus enabled to intercross with members of 

 distant colonies which swarm at the same time, and thereby increase 

 the vigour of the race — a proceeding essential to the prosperity of 

 any species. In many ants, especially those of tropical climates, the 

 workers, again, are of two classes, whose structure and functions are 

 widely difFerent. In some species they are wonderfully unlike each 

 other, and constitute two well-defined forms of workers. In others 

 there is a gradation of individuals between the two extremes. The 

 curious differences in structure and habits between these two classes 

 form an interesting but very difficult study. It is one of the great 

 peculiarities of the Saiiba Ant to possess three classes of workers. 

 My investigations regarding them were far from complete. I will 

 relate, however, what I have observed on the subject. 



*'When engaged in leaf-cutting, plundering farinha, and other 

 operations, two classes of workers are always seen. They are not, it 

 is true, very sharply defined in structure, for individuals of inter- 

 mediate grades occur. All the work, however, is done by the indi- 

 viduals which have small heads, whilst those which have enormously 

 large heads, the worker-majors, are observed to be simply walking 

 about. I could never satisfy myself as to the function of these 

 worker-majors. They are not the soldiers or defenders of the work- 

 ing portion of the community, like the armed classes in the Termites 

 or White Ants, for they never fight. The species has no sting, and 

 does not display active resistance when interfered with. I once 

 imagined they exercised a sort of superintendence over the others ; 

 but this function is entirely unnecessary in a community where all 

 work with a precision and regularity resembling the subordinate 

 parts of a piece of machinery. I came to the conclusion at last that 

 they have no very precisely defined function. They cannot, how- 

 ever, be entirely useless to the community ; for the sustenance of an 

 idle class of such bulky individuals would be too heavy a charge for 

 the species to sustain. I think they serve, in some sort, as passive 



Ann.^ Mag. N. Hist. Ser.3. Vol.^v.. 26 



