Oecophylla smaragdina, commonly known as the Asian weaver ant, green ant, or green tree ant, is an insect species renowned for its organized social structure and sophisticated nest-building. These ants construct intricate shelters by meticulously stitching together living leaves, showcasing an advanced form of natural architecture.
Identification and Distribution
Worker ants of Oecophylla smaragdina exhibit distinct differences in size, known as worker polymorphism. Larger “major” workers measure 8 to 10 millimeters, while smaller “minor” workers are 5 to 7 millimeters. The coloration of these ants can vary, appearing orange, reddish, or yellowish-brown, though Australian populations are known for a bright green gaster, or abdomen.
The queen, the largest member of the colony, usually spans 20 to 25 millimeters and is greenish-brown, although her color can also range from bright green to yellow or light brown. These arboreal ants thrive in humid tropical to subtropical forest environments. Their natural range extends across tropical Asia and Australia, encompassing regions from India, through Indonesia and the Philippines, to the Northern Territory and Queensland in Australia, as well as parts of Melanesia.
Unique Nest Construction
The most remarkable feature of Oecophylla smaragdina is its unique nest construction method, which involves an extraordinary cooperative effort. Worker ants form living chains, linking legs and bodies to pull and hold living leaves into desired shapes. This collective strength allows them to bend and secure leaves that would be impossible for a single ant to manipulate.
Once the leaves are positioned, workers retrieve larvae. Larvae possess specialized silk glands, which they use to spin cocoons before pupating. Adult worker ants squeeze the larvae, stimulating them to excrete a strong, fine silk thread. The workers then use silk-producing larvae as living “glue guns,” applying the silk to bind the leaf edges together.
Thousands of silk threads are woven to form durable, waterproof sheets that secure the leaves, creating elliptical or tent-shaped nests that can exceed half a meter. This sophisticated use of larvae as tools for construction is considered a rare and impressive example of tool use among animals. The entire process of building even large nests can be completed with remarkable speed, sometimes within a single day.
Colony Structure and Behavior
Colonies of Oecophylla smaragdina are polydomous, meaning a single colony occupies multiple nests across several trees. These expansive colonies can grow to impressive sizes, sometimes containing up to half a million individual ants spread throughout hundreds of interconnected nests. While most colonies typically feature a single egg-laying queen located within a main nest, some populations, particularly in the Australian Northern Territory, have been observed to exhibit polygyny, housing multiple queens within a colony.
The colony operates with a clear division of labor among its castes. Major workers are primarily responsible for defending the colony’s territory and foraging for food outside the nests. Minor workers, on the other hand, typically remain within the nests, where they focus on caring for the queen and the developing brood, including eggs, larvae, and pupae. They also tend to honeydew-producing insects, which supplement the colony’s diet.
These ants are highly territorial and display aggressive behavior towards intruders. When threatened, they do not sting, but instead deliver a painful bite. They spray formic acid from their abdomens into the wound.
Ecological Role and Human Interaction
Oecophylla smaragdina plays a significant role in its tropical ecosystems, primarily as a formidable predator of various insects and other arthropods. Their diet includes a wide range of prey such as beetles, flies, hymenopterans, caterpillars, thrips, and fruit flies. They also maintain symbiotic relationships with honeydew-producing insects like aphids and scale insects, which provide a carbohydrate-rich food source.
Humans have long recognized the benefits of these ants, particularly their value as natural biological control agents in agriculture. Farmers in regions like China have utilized them for centuries, dating back to at least 304 AD, to protect crops such as citrus, cashew, cocoa, mango, and coconut from various pests. Their presence can lead to reduced pest damage, improved fruit quality, and a decreased need for chemical pesticides.
Beyond pest control, the larvae and pupae of Oecophylla smaragdina are considered a delicacy in some cultures, such as in Thailand and Indonesia, where they are consumed for their creamy, sour, and lemony flavor. These immature stages are also commercially harvested as a protein-rich food source for captive songbirds and as fishing bait. Despite their benefits, the ants’ aggressive nature can be a nuisance for agricultural workers during harvesting.