Green Ant

Green Tree Ant

Green tree ants (Oecophylla smaragdina) make their home primarily in northern Australia, but can also be found in parts of Southeast Asia and India. They are also known as weaver ants because they make nests by weaving together green leaves with a form a silk. These ants have one of the highest social orders of any insect. Green tree ants are so-named because they live only in trees, and although they have a yellow thorax and legs, their abdomen is bright green.


Weaver ants are highly social insects, living in ordered colonies that can consist of over one-hundred nests spanning several trees and more than 500,000 individual ants. Most of the colony is made up of major and minor workers. Major workers have a length of 8 to 10 millimetres, whereas minor workers are from 4 to 5 mm. The primary duties of major workers are as soldiers, foragers of food, and colony expansionists. Minor workers tend to stay inside the colony caring for larvae and milking dietary honeydew out of small insects.

Green tree ants are territorial and highly aggressive in defence of themselves and their home. They have a strong and painful bite that is intensified by its ability to spray formic acid into the wound. Some natural or organic farmers have begun to implement green tree ants as a form of natural pest control because they will kill harmful insects as invaders while leaving crops untouched.

Classification

Green tree ants are classified under the family Formicidae in the Hymenoptera order. Some classification systems include a subfamily of Formicinae and a tribe of Oecophyllini between family and genus. Their genus is Oecophylla. Oecophylla smaragdina, Australian green tree ants, are but one species of 17 in the genus. It is indeterminate how long Oecophylla smaragdina has existed as a species, but the genus is believed to be up to 55 million years old. Australian green tree ants can be found in the tropical areas along the northern coast south to Broome in the west and Rockhampton in the east.

The Colony

All colonies are founded by and presided over by queens in the species. A single colony may have more than one queen. Queens are generally alone when they found a new colony. They choose a healthy leaf on which to lay their first set of eggs. A queen cares for her first eggs and larvae alone, feeding and protecting them until maturity. These first larvae grow into workers, and immediately begin weaving leaves together to form a nest. All subsequent eggs and larvae are cared for by the workers. More nests are constructed as the colony grows larger. Green tree ants communicate with each other through the use of chemical signals. This communication allows them to complete complex tasks efficiently as a single unit.

Nest Construction

One of the most remarkable features of weaver ants is their ability to build nests out of the leaves of the trees where they live. This phenomenon was first noted by Joseph Banks, the naturalist who accompanied Captain James Cook in his 1768 expedition to Australia. The ability to build these complex nests has attributed to their long existence and success through ecological changes occurring over millions of years. Constructing the nests requires a great deal of cooperation. Workers pull together the edges of the leaves in units and often create long chains of ants to reach leaves extending far from the branch. Once the edges of the leaves are brought together, they use silk from the larvae to bind them together. Single leaves can be left as an operable nest, or several leaves can be joined together in a modular fashion.

Crop Control

Some natural farmers use green tree ants to control harmful pests that can affect crops. These ants consume large amounts of harmful pest insects. Some studies show that trees protected by weaver ants produce higher-quality fruit. Some say that there is a drawback in that the ants also drive away beneficial insects that help in pollination.


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