CHAP. IV] FIGHTING ANTS 113 



The fire-ants, of which I have above spoken, are 

 generally found on a species of small tree or sapling, 

 with a greenish trunk. They bend the whole body as 

 they bite, the tail and head being thrust downward. A 

 few seconds after the bite the poison causes considerable 

 patin ; later it may make a tiny festering sore. There is 

 certainly the most extraordinary diversity in the traits 

 by which nature achieves the perpetuation of species. 

 Among the warrior and predaceous insects the prowess 

 is, in some cases, of such type as to render the possessor 

 practically immune from danger. In other cases the 

 condition of its exercise may normally be the sacrifice 

 of the life of the possessor. There are wasps that prey 

 on formidable fighting spiders, which yet instinctively 

 so handle themselves that the prey practically never 

 succeeds in either defending itself or retaliating, being 

 captured and paralyzed with unerring efficiency and 

 with entire security to the wasp. The wasp's safety is 

 absolute. On the other hand, these fighting ants, in- 

 cluding the soldiers even among the termites, are fran- 

 tically eager for a success which generally means their 

 annihilation ; the condition of their efficiency is abso- 

 lute indifference to their own security. Probably the 

 majority of the ants that actually lay hold on a foe 

 suffer death in consequence ; certainly they not merely 

 run the risk of, but eagerly invite, death. 



The following day we descended the Sao Louren90 

 to its junction vdth the Paraguay, and once more began 

 the ascent of the latter. At one cattle-ranch where we 

 stopped, the troupials, <or big black-and-yellow orioles, 

 had built a large colony of their nests on a dead tree 

 near the primitive little ranch-house. The birds were 

 breeding ; the old ones were feeding the young. In 

 this neighbourhood the naturalists found many birds 



