Army ants are a captivating group of insects known for their distinctive collective behaviors and nomadic existence. These ants exemplify complex social organization within the insect world. Their coordinated movements and unique life cycles make them a subject of interest in ecological studies.
Distinct Characteristics
Army ants are defined by shared characteristics, including a predatory nature, massive colonies, and a nomadic lifestyle. Unlike many other ant species, they do not construct permanent nests. Colonies can number hundreds of thousands to several million individuals.
A single queen, which is wingless, leads each colony and can produce millions of eggs monthly, ensuring synchronized brood cycles. Army ants exhibit polymorphism, meaning they have different physical forms for specialized tasks. Worker ants vary in size, with larger soldiers possessing disproportionately large heads and mandibles used for defense and dismembering prey. Most army ant workers are nearly blind, relying on chemical signals called pheromones for communication and navigation. The term “army ant” encompasses over 200 species found globally.
Nomadic Lifestyle and Hunting Swarms
Army ants cycle between two main phases: a nomadic phase and a stationary phase, tied to the queen’s reproductive cycle. During the nomadic phase, which lasts approximately 15 days, the colony is constantly on the move, foraging daily to feed developing larvae. At dusk, they form a temporary nest called a bivouac, built from their interconnected bodies. This living structure houses the queen and brood, providing protection and chambers within the ant mass.
The nomadic phase ends when larvae pupate, beginning the stationary phase, which lasts about two to three weeks. During this period, the queen’s abdomen swells, and she lays a large number of eggs; the colony remains in one bivouac. Once the new generation of workers emerges from pupae, the colony resumes its nomadic foraging. Army ants are known for their “swarm raids,” where thousands to millions of ants move together in a fan-shaped front, overwhelming prey. These coordinated expeditions can cover 100 to 200 meters daily, consuming up to 500,000 prey animals, including insects, spiders, and small vertebrates.
Global Distribution and Habitat
Army ants are primarily found in tropical and subtropical regions. Their distribution spans South America, Central America, Africa, and Asia, with some species extending into the southern United States. These ants inhabit a variety of environments, predominantly thriving in hot and humid tropical rainforests. They can also be found in scrub forests and swamp areas.
Encountering Army Ants
Encounters with army ants are uncommon, but understanding their behavior can alleviate concerns. While their foraging swarms are formidable to their prey, army ants are generally not aggressive towards humans unless provoked or trapped. Their primary diet consists of other insects and small vertebrates, not larger animals or humans. If an army ant does bite, it can be painful, similar to a needle prick, but causes only mild discomfort and is not life-threatening.
Their mandibles are adapted for cutting hard-bodied insects, making them ineffective against human skin. If a swarm is encountered, it is advisable to step around their foraging columns and avoid disturbing them. Army ants are nomadic and will continue to move, so they rarely remain in one location for an extended period.