themselves. There is a single queen per colony, who
remains in the bivouac except when the entire army
is on the move, at which time an entourage of workers
and soldiers transports her.
Eciton raiders stream from the bivouac, making
a dense column in search of prey. Soon the column
begins to fan out widely, raiding parties moving in
different directions. Ants move over and through the
forest litter. Though virtually blind, the ants effectively
communicate by chemical signals, and once prey is
discovered, ants quickly converge upon it. Small prey
is killed and taken to the nest, large prey is killed,
dismembered, and carried to the nest, each task
carried out by a specific worker caste. The raiders do
not restrict their plundering to animals on the ground.
They sometimes climb trees, even ascending into the
canopy. They will enter human dwellings and attack
cockroaches and other small animals.
Eciton burchelli is a generalist predator. Prey consists
of anything alive and small enough to subdue, most
commonly arthropods such as caterpillars, spiders,
millipedes, and other animals found among litter and
leaves. Small vertebrates such as tree frogs, salamanders,
lizards, and snakes are routinely attacked, and baby
birds in the nest are frequent army ant victims.
Note that humans are not included among the
prey items of army ants. Many tropical visitors are
concerned about possibly being attacked by army ants,
but that worry is unfounded. The ants are easily spotted
crossing a trail and thus easily avoided. Watching
an army ant swam in action, with its attendant birds
(discussed next), is a thrilling experience.Here Come the Antbirds
Raiding parties of army ants attract attention from
diverse groups of birds specialized in following army
ants. Birds typically and noisily accompany the ant
swarms and capture prey exposed or attempting to flee
from the horde of army ants. One of the easiest ways to
find an army ant swarm is to listen for the bird sounds.
Neotropical antbirds are members of two families,
Thamnophilidae (206 species) and Formicariidae (62
species). These are discussed more in chapter 15. They
are called antbirds because some follow and associate
with army ant swarms. However, the vast majority of
the species so designated do not follow army ants or
attend ant swarms. Only 30 species from the two families
combined are considered “professional” ant- following
species, strongly associated with army ant swarms (plate
10- 38). In addition, numerous other species of birds,
including various woodcreepers, tanagers, motmots, and
ground cuckoos join antbirds in attending ant swarms.
The ant- following birds devour arthropods and small
vertebrates (prey preference depending on the bird’sPlate 10- 38. The Bicolored Antbird (Gymnopithys bicolor), here
alertly looking for prey flushed by an army ant swarm, was
recently split from the White- cheeked Antbird (G. leucapsis).
This Photo by Kevin Zimmer.
Plate 10- 39. The Ocellated Antbird (Phaenostictus mcleannani)
and its feathered colleagues appear to be parasites of army
ants, reducing their booty and paying them nothing in return.
So much for mutualism, in this case. Photo by Kevin Zimmer.178 chapter 10 tropical intimacy: mutualism and coevolution