6i4 LIFE : OUTLINES OF GENERAL BIOLOGY 



But this is only half of the story. While the tug of peace is going 

 on, other workers get hold of larvae, gripping the soft body of the grub 

 by the middle. Now, the grub of an ant has got what the parent 

 has lost — namely, a couple of silk-glands opening at the mouth. 

 The ordinary use of these is to form a silken cocoon, within shelter 

 of which the grub changes into an ant. The cocoons, or pupa-cases, 

 are popularly called "ants' eggs"; but this is, of course, very bad 

 natural history. The cocoon-making is usually finished in one day, 

 and the glands do not need to be very large ; but in the grub of the 

 tailor-ant they are unusually big and can make a lot of silk. So it has 

 come about that the worker-ant with the grub in its mouth is able 

 to dab it against one leaf and then carry it over to the other leaf, 

 thus drawing out a thread of glutinous silk. 



Several workers do this over and over again, and the result is a 

 sort of web of silk binding two or three leaves together. Some 

 naturalists have compared the silk-producing larva to a shuttle and 

 the worker to a weaver; others speak of the larva as the worker's 

 needle and thread. In some ways it would be nearer the mark to 

 say that the larva serves as a living gum-bottle. But the result is a 

 web, an essential part of the nest. 



In contrast to the rough-and-ready nest-tangles, there are master- 

 pieces. Thus Forel has in his collection a triangular tree-nest about 

 eight inches high and six inches at the base, a substantial but very 

 light construction woven among the leaves. The detailed architecture 

 is extraordinary, for the nest consists of a large number of adjacent 

 and superposed compartments, each a little under half an inch 

 across and about a fifth of an inch in height, all bound together by 

 minute pillars and beams. This would be striking enough if it were 

 made of chewed wood or salivated earth, after the fashion of the 

 termitaries which the so-called "white ants" construct. But this 

 masterpiece is woven out of silk. It would be striking enough if it 

 were made by a spider, though their webs are often triumphs of 

 instinctive art. But the spider makes its own silk, whereas this so- 

 called tailor-ant is using its larvae all the time ! 



Dr. Goeldi, who found the nest in Brazil, noticed the workers 

 repairing some compartments that had been slightly damaged, and 

 each had a grub in its jaws. A very quaint detail was that the nest 

 included another nest, which belonged to a minute bee. The ants 

 had simply included the bee's tiny construction between their own 

 nest and the leaves of the branch. The association seemed to be 

 quite amicable, "wheels within wheels" again. F'orel calls it "pacific 

 parabiosis", but by any other name it would sound as surprising! 



.\mong the most striking tailor-ants are the large and handsome 

 members of the genus Polyrhachis, deserving a more usable name. 

 Some of them have a golden-yellow breast and a burnished -black 

 hinder body; others have a biirnished-black breast and a golden- 



