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Greentree Ants Program

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Copyright David Paul, University of Melbourne.
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The green tree ant belongs to the ant genus Oecophylla (subfamily Formicinae) which consists of only two species; O. longinoda and O. smaragdina. Oecophylla smaragdina is found in the tropical coastal areas in Australia as far south as Rockhampton and across the coastal tropics of the Northern Territory down to Broome in West Australia. Green ants are also often referred to as weaver ants because of their ability to weave leaves together to form nests bound with silk produced by their larvae. Most of the nest construction and weaving is conducted at night with major workers weaving towards the exterior of the nests and minor workers weaving within the interior.

A mature colony of green tree ants can hold as many as 100,000 to 500,000 workers and may span as many as 12 trees and contain as many as 150 nests. Green ant colonies have one queen and a colony can live for up to eight years. Minor workers usually remain within the egg chambers of the nest tending the larvae, whereas major workers defend the colony territory, assist with the care of the queen and forage.

Mimetic relationships between spiders and ants

Chemical Mimicry

Several species of spider live with green ants such as the salticid spider Cosmophasis bitaeniata. Salticid spiders, or jumping spiders, as they are sometimes referred to, have excellent eyesight and are only active during daylight, weaving a protective silken cocoon to spend the night in. Interestingly, this spider does not look like green ants but instead it chemically mimics green tree ants.


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Chemical mimicry evolves for a variety of reasons. In the case of the salticid and the green ant the mimicry is deceptive and exploitative. The spider is infact disguising itself as an ant and then accessing the green ants nests to feed upon their larvae. This is achieved because green ants do not have good vision and circumnavigate their surroundings by scent, smelling everything with their antennae. Consequently, the ants think the spider is another ant and ignore its presence within the nest. The distribution of these spiders is aligned with the distribution of green ant nests with the greatest number of spiders being found in the older nests with a higher percentage of dead leaves and less major ant workers. In addition, and as seen in the photo below, the spider lays its egg sac alongside the green ants nest so the emerging spiderlings can readily access the green ant larvae to prey upon. The green ant larvae provide the spider with its deceptive chemical scent. This spider is very common in Townsville and far north Queensland generally.

Copyright David Paul, University of Melbourne. Fee free license image


Visual Mimicry

Copyright GEO Magazine

Selection pressure exerted by visually hunting predators such as birds and wasps who ordinarily hunt spiders results in spiders evolving over time to visually resemble ants. The species of spider below is from the family Thomisidae and is called Amyciaea albomaculata. This species hunts at dusk and night and preys specifically on green tree ant major workers, hanging on a drag line of silk to consume their prey at leisure. Notice the false eye spots on the spider’s abdomen and the raised front forelegs which are thought to mimic the green ants raised antennae. Cairns is a good place to find these very fast moving spiders.

A second less common spider is shown below preying upon a green tree ant major worker. This spider is from the family Theridiidae and it spins a web to capture green ants in. The silk is thought to attract green ants that bite it and get catapulted into the spider’s web. Here, the green ant is isolated from its nest mates who cannot defend it and the spider is in control, biting and immobilising its prey.

Spider eating an ant
Copyright GEO Magazine

Aggressive Behaviour

Major workers are typically aggressive towards intruders, as depicted in the photo below, and vigorously defend their nests. This aggression is towards all species including other green ants from neighbouring nests. Consequently green ants reduce the numbers of insects on the trees they inhabit. This is why green ants are sometimes referred to as biological control agents reducing the damage that other insects do, for example, to the citrus and mango trees they inhabit.

Despite the fact that green ants are aggressive and attack other insects, several species of insect and spider live with green ants, either as a visual mimic or a chemical mimic of green tree ants.

Copyright David Paul, University of Melbourne.
Fee free license image




Allan RA, Elgar MA (2001) Exploitation of the green tree ant Oecophylla smaragdina by the salticid spider Cosmophasis bitaeniata.
Australian Journal of Zoology 49: 129-139

Allan RA, Capon RJ, Brown V, Elgar MA (2002) Mimicry of host cuticular hydrocarbons by a spider that preys on ant larvae.
Journal of Chemical Ecology 28: 835-848

Allan RA, Elgar, MA and Capon, RJ (1996) Exploitation of an ant chemical signal by the zodariid spider Habronestes bradleyi Walckenaer. Proceedings of the Royal Society of London Series B 263, 69-73.

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