80 ON THE HABITS OF ANTS. [LECT. 



analogous to that of Polyergus, but it is one in which 

 slave-owning has almost degenerated into parasitism. 

 It is not, however, a case of true parasitism, because 

 the Tetramoriums take great care of the Aner gates, 

 and if the nest is disturbed, carry them off to a place 

 of safety. 



M. Forel, in his excellent work on ants, has pointed 

 out that very young ants devote themselves at first to 

 the care of the larvae and pupae, and that they take no 

 share in the defence of the nest or other out-of-door 

 work until they are some days old. This seems natural, 

 because at first their skin is comparatively soft ; and it 

 would clearly be undesirable to undertake rough work, 

 or run into danger, until their armour had had time to 

 harden. There are, however, reasons for thinking that 

 the division of labour is carried still further. I do not 

 allude merely to those cases in which there are com- 

 pletely different kinds of workers, but even to the 

 ordinary workers. In L. flavus, for instance, it seems 

 probable that the duties of the small workers are some- 

 what different from those of the large ones, though no 

 such division of labour has yet been detected. 



One of the most interesting problems with reference 

 to ants is, of course, to determine the amount of their 

 intelligence. In order to test this, it seemed to me that 

 one way would be to ascertain some object which they 

 would clearly desire, and then to interpose an obstacle 

 which a little ingenuity would enable them to overcome. 

 With this object in view, I placed food in a porcelain 

 cup on a slip of glass surrounded by water, but acces- 

 sible to the ants by a bridge, consisting of a strip of paper 

 two-thirds of an inch long and one-third wide. Having 



