o is a good observer, a
good field naturalist, occupies at present a more important position
than ever before, and it is now recognized that he can do work which
the closest naturalist cannot do. The big-game hunter of this type and
the outdoors, faunal naturalist, the student of the life-histories of
big mammals, have open to them in South America a wonderful field in
which to work.

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 pain; 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, including the soldiers even among the termites, are frantically
eager for a success which generally means their annihilation; the
condition of their efficiency is absolute 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 Lourenco to its junction with
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 neighborhood the naturalists
found many birds that were new to them, including a tiny woodpecker no
bigger than a ruby-crowned kinglet. They had collected two night
monkeys--nocturnal monkeys, not as agile as the ordinary monkey; these
two were found at dawn, having stayed out too late.