Army Ants
Ectiton burchelli Wikipedia
https://en.wikipedia.org/wiki/Army_ant
Army ants, often called legionnaire ants, comprise roughly 200 known species worldwide, with many belonging to the New World genus Eciton. While the exact number of species inhabiting the Amazon rainforest is uncertain, they are among the most conspicuous and ecologically influential insects in the region.
These ants are obligate carnivores and highly coordinated hunters. Rather than foraging individually, army ants conduct massive group raids in which thousands to millions of individuals sweep across the forest floor. Any small animal unable to escape—primarily arthropods such as insects, spiders, and even other ant species—is quickly overwhelmed. Their raids are not random but highly organized, with distinct roles among workers of different sizes.
Nomadic Lifestyle and Living Architecture
Unlike most ants, army ants do not build permanent nests. Instead, they form temporary living structures known as bivouacs, constructed from their own bodies.
In these structures, ants link their legs and bodies together to create a protective shelter for the queen and brood. Bivouacs are often located in sheltered areas such as hollow logs or tree cavities, but their defining feature is that they are alive and constantly changing.
Army ants alternate between two behavioral phases:
Nomadic phase: frequent movement, daily raids, and relocation of the bivouac
Stationary phase: reduced movement while the queen lays eggs and larvae develop
This cyclical lifestyle allows them to exploit resources efficiently while avoiding overexploiting any single area.
Keystone Predators of the Rainforest
Army ants are widely considered keystone species due to their outsized impact on ecosystem dynamics. By preying heavily on other arthropods—including dominant species like leafcutter ants—they help regulate populations and maintain ecological balance.
Their influence extends far beyond direct predation. As army ant swarms move through the forest, they flush out fleeing insects and small animals. This creates feeding opportunities for a diverse community of followers, including birds, reptiles, amphibians, and even some mammals.
Some bird species, particularly antbirds, are so specialized that they rely heavily on army ant raids for food. Without army ants, these species would struggle to survive—highlighting the ants’ role as both predator and ecosystem facilitator.
Vulnerability to Habitat Fragmentation
Despite their ecological importance, army ants are highly sensitive to environmental change. Their nomadic lifestyle requires large, continuous tracts of forest. When forests are fragmented by deforestation, agriculture, or roads, army ant colonies may be unable to complete their migration cycles or sustain their large populations.
Research suggests that species like Eciton burchellii decline sharply in fragmented habitats, making them useful indicator or umbrella species for conservation in Neotropical forests (Perez-Espona, 2021). Protecting army ants often means protecting entire ecological networks.
Myths vs. Reality
Army ants have long been sensationalized in popular media. The film The Naked Jungle famously portrays them as unstoppable forces that consume everything in their path, including crops, buildings, and large animals.
In reality, this is a significant exaggeration. Army ants are strictly carnivorous and primarily target small, soft-bodied prey. They do not consume vegetation, and they pose little threat to large animals or humans beyond defensive bites if disturbed.
References:
Army Ant New World Encyclopedia
https://www.newworldencyclopedia.org/entry/Army_ant
Perez-Espona, Silvia.(March, 2021) Eciton Army ants-Umbrella species for conservation in neotropic forests Diversity