Army Ant

Overview

The Army Ant (Eciton burchellii), widely feared and revered across the Neotropics as the ultimate predatory superorganism, is an iconic nomadic ant that conducts the largest, most spectacular swarm raids in the animal kingdom. Roaming the shadowy floor of Central and South American tropical rainforests, a single colossal colony contains between 300,000 and 700,000 blind, highly coordinated workers. Rather than building permanent subterranean nests, army ants are entirely nomadic, marching relentlessly through the jungle and assembling temporary architectural nests—called ‘bivouacs’—constructed entirely from their own living, interlocking bodies.

Operating as a premier keystone predator of the rainforest understory, a single Eciton burchellii colony consumes up to 30,000 prey items every day. Their massive swarm raids advance in a terrifying, 65-foot-wide (20-meter) carpet across the forest floor, flushing out and devouring every insect, spider, scorpion, and small vertebrate in their path. Furthermore, an entire ecological community of over 300 specialized animal species—including antbirds, woodcreepers, parasitic flies, and rove beetles—relies obligately on army ant swarms to flush out prey, making them foundational to Neotropical biodiversity.

Equipped with massive, fishhook-shaped mandibles, their ferocious soldiers are legendary throughout the Americas.

Biology and Physical Characteristics

The physical castes of Eciton burchellii represent extreme morphological specialization. The worker force is polymorphous, ranging from tiny media workers to monstrous, pale-headed soldiers (submaculates) equipped with enormous, ice-tong-like sickle mandibles that can pierce human skin with ease. Because all workers and soldiers are completely blind (possessing only rudimentary, vestigial light-sensing eye spots), communication and navigation are mediated entirely through volatile chemical pheromones laid down by scout ants. To construct a bivouac, thousands of workers lock their tarsal leg claws together around the queen and brood, forming an insulated, temperature-controlled living sphere of hanging ants.

Behavior and Ecology

The life of an army ant colony follows a strict 35-day cycle split into two phases: the nomadic phase and the statary phase. During the 15-day nomadic phase, the colony moves every single night to a new bivouac site, conducting voracious daytime fan-shaped swarm raids. During the 20-day statary phase, the colony remains in a single hollow tree or log while the single, permanently wingless queen swells with eggs, laying an astonishing 100,000 to 300,000 eggs in a single week while the previous brood pupates. Indigenous Amazonian peoples historically used soldier army ants as surgical sutures: clamping the ant’s mandibles across an open wound before twisting its body off, leaving the locked jaws as natural stitches.

Conservation and Human Impact

Eciton burchellii is common and secure across extensive rainforest reserves throughout Central and South America. However, because each colony requires an expansive, unfragmented territory of several hundred hectares to sustain its intense daily foraging raids, habitat fragmentation from cattle ranching and deforestation poses severe localized risks to colony survival.

Interesting Factoid

Army ants do not build nests out of mud or wood: instead, over half a million living ants lock their legs together with their claws to build a giant hanging fortress out of their own living bodies, complete with tunnels, nurseries, and chambers for their queen.