Deep in the canopy of Southeast Asian rainforests lives Colobopsis explodens, an ant species with a highly unusual survival strategy in the insect world. The ant species is capable of exploding its own body to destruction when facing an immediate threat.
The species was officially introduced to the scientific world in April 2018 through a publication in the journal ZooKeys. The study established Colobopsis explodens as the primary model species for studying the phenomenon of exploding ants in Southeast Asia.
The exploding ant is endemic to the Borneo tropical rainforest across Malaysia and Indonesia. They spend most of their time high up in tree canopies. In such areas, the ant frequently encounters other species in its foraging territory.
When feeling cornered by an enemy attack, a minor worker ant sacrifices its own life by exploding to incapacitate the adversary.
The Mechanism of Autothysis
The self-explosion phenomenon in social insects is known in biology as autothysis. The term refers to a mechanical process where an organism sacrifices itself through the deliberate rupture of its own body wall.
Colobopsis explodens belongs to the Colobopsis cylindrica (COCY) species group, a Southeast Asian ant group known for possessing greatly enlarged specialized glands running along their bodies. Close relatives within this complex include Colobopsis cylindrica and Colobopsis badia.
The act of sacrifice begins when a minor worker feels pressed by an enemy. The minor workers contract the muscles around their abdominal cavity with extreme force to generate high internal pressure.
That high pressure shatters the integrity of the ant's outer skin or exoskeleton within seconds. The physical explosion instantly ruptures the ant's vital tissues while simultaneously releasing the contents of its body toward surrounding enemies.
Hypertrophied mandibular glands serve as the main organ rupturing during the process. Running along the length of the ant's body, these specialized glands hold an abundant volume of liquid ready to be expelled upon body rupture.
How Their Toxic Liquid Disables Enemies
The discharge from the body of Colobopsis explodens produces a thick, bright yellow liquid secretion. The substance acts like a strong adhesive that hardens quickly upon exposure to open air.
Insects hit by the spray immediately lose their mobility. The sticky liquid glues their legs and antennae together, bringing the attack to a sudden halt.
Laboratory analyses show that the liquid is rich in phenolic compounds and aliphatic derivatives. These chemical components induce severe irritation while damaging the body tissues of the targeted enemy.
Enemies sprayed by the liquid are not merely trapped in glue, but also exposed to its toxins. The effect immediately immobilizes the rivals before they can advance further.
Distinct Roles of Minor Workers and Major Workers
The suicidal exploding behavior is performed exclusively by the minor worker caste while patrolling foraging grounds outside the nest. Inside the colony, major workers take on a completely different form of defense.
The major workers are slightly larger, reaching up to 8.7 millimeters in length. They feature a large, round, plug-like head structure built specifically to perform phragmosis, the act of physically blocking access into the nest.
The flattened head size of major workers fits precisely into the diameter of nest entrance holes located in wooden cavities.
Blocking the entrance with their plug-like heads prevents intruders that bypass minor workers outside from entering the reproductive chambers.
Reference:
Laciny, A., et al. (2018). Colobopsis explodens sp. n., model species for studies on "exploding ants" (Hymenoptera, Formicidae), with biological notes and first illustrations of males of the Colobopsis cylindrica group. ZooKeys, 751, 1–40.
