The carnivorous beetles, or Carabidae, appear
in extremely few numbers within the tropics: this is the more
remarkable when compared to the case of the carnivorous quadrupeds,
which are so abundant in hot countries. I was struck with this
observation both on entering Brazil, and when I saw the many
elegant and active forms of the Harpalidae reappearing on the
temperate plains of La Plata. Do the very numerous spiders and
rapacious Hymenoptera supply the place of the carnivorous beetles?
The carrion-feeders and Brachelytra are very uncommon; on the other
hand, the Rhyncophora and Chrysomelidae, all of which depend on the
vegetable world for subsistence, are present in astonishing
numbers. I do not here refer to the number of different species,
but to that of the individual insects; for on this it is that the
most striking character in the entomology of different countries
depends. The orders Orthoptera and Hemiptera are particularly
numerous; as likewise is the stinging division of the Hymenoptera;
the bees, perhaps, being excepted. A person, on first entering a
tropical forest, is astonished at the labours of the ants:
well-beaten paths branch off in every direction, on which an army
of never-failing foragers may be seen, some going forth, and others
returning, burdened with pieces of green leaf, often larger than
their own bodies.
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