BIOPSYCHOLOGICAL 615 



yellow hinder body, and others are old-gold all over; for so the 

 changes are rung among species. But we are concerned just now 

 with the nests. One of them, from Java, consists of many compart- 

 ments, as in the preceding nest from Brazil; but the workers have 

 utilised the silken web as a basis for intermingling minute fragments 

 of leaf and stem and bark. The result is a flexible brown contraption, 

 half silk, half debris, sometimes among the leaves of a palm, and 

 sometimes among the grass. 



In this case the ants are not carnivorous like those we started 

 with; but they keep small coccus insects as domesticated animals, 

 and use the surplus nutritive materials of these "cows" as part of 

 their own sustenance. Jakobson, who noticed this in Java, found 

 little stables beside the main nest — the bjTes for the cattle. And 

 these little stables have also their silken foundation, furnished by 

 the larvae. 



It is interesting to notice the great variety of nests in this one 

 genus (Polyrhachis) of handsome tailor-ants. Some consist entirely 

 of woven silk; some have fragments of plants added to the silken 

 web; some have a silk fabric which serves as the foundation for a 

 superstructure of papier mache. In some species the nest is a one- 

 roomed house; in others there are numerous rooms. There are also 

 miniature nests, less than an inch long and hardly half an inch 

 broad, almost as simple as sleeping-sacs, but covered outside with 

 greyish lichen. One could almost predict where they are found — 

 pressed against the bark of a tree. Everywhere we get the impression 

 of living creatures as experimental, proving all things and holding 

 fast that which is good. For all the kinds of nests that we have 

 mentioned in this section are made by species of one genus. This is 

 specificity in behaviour. 



But the most remarkable fact, after all, is the central one, that 

 the worker-ants use their baby-sisters to make the silken web. 

 Whether we compare the larvae to shuttles, or to needle and thread, 

 or to animated gum-bottles, the fact stands out that the workers 

 are using other creatures — their own kith and kin, to be sure — as 

 tools. Do any other creatures besides man utilise other living crea- 

 tures as tools ? Is this a unique case ? 



Everyone would like to know how the strange custom arose. 

 Even if we emphasise the fact that ants are, in the main, children 

 of instinct, we may suppose that individuals put inborn non- 

 intelligent inspirations or initiatives to the test of experience, and 

 stick to those that pay. It is probably safe to conclude that the 

 utilisation of the larvae did not occur to the ancestors of the tailor- 

 ants as a bright idea. This is too generous. It is more likely that the 

 custom arose as an extension of something else, and was adopted 

 after it was tested. That something else might be, as Forel suggests, 

 the custom that ant-workers in general have of cleaning the cocoons 



