Geoscience Reference
In-Depth Information
geologic and climatic changes and are extremely resilient to environmental
changes. They play a vital role in the maintenance of the tropical rainforest as polli-
nators and decomposers, and they provide essential nutrition to myriad animals
that inhabit the forest. The actual number of insects within the tropical rainforest is
unknown. Several studies have documented thousands of species present on a sin-
gle tree. By extrapolating these numbers to the larger forest, estimates of hundreds
of thousands of species are thought to inhabit the rainforest. Although not all of the
species identified within the Neotropical rainforest can be addressed in detail in
this volume, a few groups will be examined.
Ants (order Hymenoptera) play a crucial role in destroying and recycling vege-
tation; others are carnivorous and able to strip a small animal in minutes. Leaf-cut-
ter ants are a subgroup of the fungus-growing ants (Formicidae) present only in the
Neotropics. They are thought to have evolved in the wooded and savanna areas of
South America and to have diversified to take advantage of the lush vegetation of
the rainforest. Large, strong worker ants climb selected trees, cut out small sections
of leaves or flowers with their sharp mandibles, and carry them great distances to
their nests. They use the leaves as organic mulch to nurture the growth of mycelial
fungus—their sole source of food.
Army ants are swarming ants that are most abundant in the Neotropics and
Africa. Army ants are social ants with a queen, soldiers, and worker classes. They
form large colonies. Populations within one group can reach in excess of 1 million
individuals. They can be orange to dark red, brown, or black. Neotropical army
ants are nearly blind, and they communicate by chemical signals. Nomadic, they
only stop at underground nests or in hollow logs during their reproductive cycles.
Typically, one queen stays at the nest until the next move. Army ants practice
group predation—the pack swarms their prey, killing and dismembering it to bring
it back to their temporary nest. Army ants hunt on the ground and in trees. Prey
includes caterpillars, spiders, millipedes, small frogs, lizards, salamanders, snakes,
and small birds. Army ants conduct mass raids during which they remove large
amounts of food. A single colony can harvest up to 90,000 insects during one day.
Bullet ants are large tropical ants. They can be as large as 1 in (3 cm) long. Their
range includes Central and South America. They live at the base of trees or in tree
cavities. Their attack mode is a hard bite delivered to the prey, accompanied by a
powerful sting. The sting carries a neurotoxin that affects the nervous system of the
prey. Bullet ants tend to be solitary when hunting and will also collect nectar,
water, and plant parts, as well as arthropods, insects, and parts of small vertebrates.
Other ants have developed symbiotic relations with Neotropical plants. The
cecropia tree has leaves and fruit that many creatures find desirable, but these tasty
products are protected by Aztec ants. The tree's hollow trunk and branches provide
a home for the ants, and the tree produces Mullerian bodies, glandular nodules rich
in carbohydrates that the ants use as food. Ants consume these energy-rich capsules
and viciously attack anything that touches the plant. Only the sloth, protected
by an undercoat of dense fur, may safely climb the tree and dine on the leaves.
