Weaver ants, predation and natural control

The weaver ant, Oecophylla smaragdina F. (Hymenoptera: Formicidae), also referred to as green tree ant in a blog about their nest building behavior, is a very successful territorial predator of various arthropod preys. So successful are they that arthropods and other small animals do well to avoid their territory. Even predators learn to avoid weaver ants because of their painful bite and distastefulness.

In fact, one particular jumping spider, Myrmarachne plataleoides O. P.-Cambridge (Arachnida: Araneae: Salticidae), used this weaver ant reputation to its advantage by mimicking its form and behavior and thereby gaining protection from predators. This spider, commonly known as "kerengga ant-like jumper" stays within the tree occupied by the weaver ant and hides under its thin webbing on leaves from where it ambushes insect preys. However, it does not get any closer to the resident weaver ants, or else it becomes the latter's food.

Despite its superior abilities, weaver ants also fall prey to predators that are able to work around their defenses.

The crab spider, Amyciaea lineatipes O. P.-Cambridge (Arachnida: Araneae: Thomisidae) below takes advantage of mimicry to get near weaver ants, it's preferred prey.

Many lycaenid butterflies are closely associated with ant colonies. The moth butterfly, Liphyra brassolis Westwood (Lepidoptera: Lycaenidae), larva feed on ant larvae. Weaver ants and other tree ant species are not able to overcome the heavy shield of the moth butterfly caterpillar that protects its soft underside. Thus, this predator is able to consume ant larvae with gusto inside the latter’s own nest! Now that's what you call a truly unwelcomed guest.

A different kind of relationship with weaver ants also exists for two other lycaenid species. The first one is featured in Butterflies of Singapore: Arhopala centaurus nakula , while the second is an unspecified lycaenid species seen in a video below from Animal Planet.

A discussion about weaver ant predation won't be complete without predation by humans.  Many regions in Southeast Asia consider the immature stages (often referred to as eggs only, when it fact they are composed of eggs, larvae and pupae) of the weaver ants as delicacy, renown for its distinctive taste.

In the Philippines, weaver ant immature stages is a delicacy in northern and central Luzon and referred to as “bu-os“.  In Thailand, prospects for weaver ant farming was determined to be potentially profitable by looking at food conversion efficiency and costing in that country.  In Indonesia, weaver ants are used as “kroto” or food for songbirds.  In Australia, nutritional information of larva and whole insect are available as weaver ants are considered wild harvested indigenous food that can be incorporated in one’s diet.

Weaver ants have also been used as biological control agent against orchard arthropod pests. Successes have been known such as those reported in programs for Australian cashew and mango plantations and Vietnamese citrus plantation. What excites food security researchers the most are the possibilities of turning harmful orchard pests into valuable protein for human consumption (entomophagy), and accomplishing both without the need for expensive input or high technology.

Indeed, what is regarded by many as pest in urban and rural areas might turn out to be doubly beneficial in our common concern for global food security and the environment.

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