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Tales from the woodpile #2

August 25, 2013
Annoy-ance

Annoy-ance

While splitting wood recently, the bark fell off a log revealing an colony of irate ants, which proceeded to scurry around with their abdomens in the air (pictured left, click image to enlarge it). They were threatening to spray formic acid (methanoic acid) as a defense mechanism. The word ‘formic’ comes from the Latin word for ant, formica.

Defi-ance

Defi-ance

Most ants use a mixture of formic acid and other chemicals to defend themselves. In some ants this is delivered as a painful sting. The Dolichoderinae family of ants lack a sting and therefore spray the chemicals by forcibly ejecting the formic acid from a poison gland in the tail. A Spider Ant (Leptomyrmex erythrocephalus) (from the Greek eruthros meaning red and kephale meaning head), pictured right, is shown with the abdomen raised in a defensive position. Another local ant from the same family (pictured below) is the Double-spined Dolly Ant (Dolichoderus doriae) (from the Spanish dorados for golden colour). It is named after the spines that protrude from the thorax. Annoying either of these ants will result in a defensive spray and the familiar ‘ant smell’.

Protruber-ance

Protuber-ance

Other fauna use this ant behaviour to their advantage. Many birds, including some Australian birds such as the Regent Honeyeater, are known to perform ‘anting’ where they rub ants into their feathers. The ants get annoyed and spray formic acid, which acts as a combination insecticide, miticide, fungicide and bactericide. Some birds then eat the ant after all the formic acid has been eliminated.

In an amazing evolutionary step, creatures such as the Anteater (from the Americas) do not produce hydrochloric acid to promote digestion like most mammals. Instead they rely on the formic acid secreted by ants they eat to do the job. Hence the ants provide the acid to digest themselves.

And that is why you never see an echidna with a sore tummy. It’s full of ant-acid.

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