How the Ancient Chinese Control Pests

Everyone knows that pesticides are very harmful, but we need to eat and not everyone can afford to buy expensive clean food. Pesticides increase crop yields and are now considered essential to sustaining the human food supply. So what to do?

Currently scientists are looking for biological alternatives to pesticides. But 1,700 years ago, ancient Chinese farmers used something organic, chemical-free, pollution-free, and auto-recyclable to control pests and diseases – ants! (Ironically, today China uses more chemical pesticides than any other country.)

To protect crops, ancient Chinese farmers moved weaver ant colonies (scientific name Oecophylla smaragdina) from the wild to their orchards. This was first recorded in a botany textbook 'Plants of the Southern Regions' written by author Ji Han around AD 304. He called them orange ants. Even later, intermediaries appeared to buy ant nests in the forest and sell them to farmers.

Yellow ants are amazing animals! They live in trees and make their own nests out of leaves. Each tree can have up to a hundred nests, each containing thousands of ants.

To make new nests, worker ants look for matching leaves. Once selected, a worker ant will stand on the edge of the leaf, lift up, use its jaws to bite an adjacent leaf and pull it down to meet the first leaf. Other workers joined in, forming a line of ants to pull the leaves together. If the distance between the leaves is too large for an ant to reach, one ant will climb onto the back of another to reach further. If necessary, an ant ladder will form to widen the gap by biting the other's back with its jaws.

When the leaf edges are joined together, other ants will gently carry the larvae from the old nest. Weaver ant larvae, like silkworms, can produce silk from their salivary glands. A strong, sticky silk is produced from the proboscis on the head of the larva. The larvae are carried along the edges of the leaves to glue them together, much like using a glue gun. Hence weaver ants also known as 'weaver ants'.

The ancient Chinese used ants to control pests.

Once inside the new safe 'home', the new ant community begins to multiply. Queen ants lay eggs, which develop into larvae and pupae. From the pupae emerge worker ants. Larger worker ants leave the nest to feed. Foraging ants are very aggressive and territorial predators: they attack and kill other insects, bringing the carcasses back to the nest for food. By doing so, the weaver ants will clear the area around the host plant for other insects that may be harmful to the plant. The smaller ants tend to stay close to the house to tend to the larvae and collect the nectar secreted by nearby bugs.

The ancient Chinese must have noticed that colonies of weaver ants are beneficial to the host plant. When growing citrus and mango trees, they introduced nests of weaver ants into their orchards. This method has spread to other countries in Southeast Asia, where it is still being used today.

Modern scientific observations have confirmed that trees with weaver ants produce more, better quality fruit and are less susceptible to leaf damage by pests and diseases.

Of course, everything has a downside! Weaver ants derive a portion of their nutrition from the honeydew secreted by bugs, which feed on the juicy sap of the host plant. Overall, however, the presence of weaver ant colonies is beneficial for fruit trees.

But that's not all!

Weaver ants, especially larvae, have a lot of protein and fatty acids that are used by humans for food. Indeed, in many countries they are considered such a delicacy that weaver ant larvae cost more than beef. Ants are harvested by creating a hole in the nest and releasing fallen insects into the nest. The 'meal' will cause the worker ants to escape and leave behind the larvae. Ant eggs are also commonly used as a condiment.

Weaver ants are also used in Traditional Chinese Medicine to prevent rheumatism. In India, ants are dipped in topical oils to cure rheumatism, gout and other skin ailments. 

Weaver ants are one of the few proven good alternatives to chemical pesticides. Of the 30 million insect species out there, there must be others discovered and used to replace pesticides.