January 2016

Looks can be deceiving

This odd ant/spider was scuttling around the office and I am hoping you might be able to shed some light on what it might be.

Answer

Ant mimicking jumping spider It takes a keen eye to see through this disguise. It looks, moves and acts like an ant but it is really a jumping spider. Image courtesy: Luke CarltonAnt mimicking jumping spiderAnt mimicking jumping spider

You have found an ant-mimicking spider in the genus Myrmarachne. This literally translates as 'ant spider'. It belongs to the family Salticidae, commonly called jumping spiders. These nimble little spiders, famous for both their athletic prowess and the bright colours of many species, are common in all parts of Australia.

Some jumping spiders have evolved a striking likeness to ants. Spiders have two body parts, but insects have three, and spiders sport eight legs compared to six legs on insects. That means some modifications have been made to create the disguise. The spiders’ first body part, called the cephalothorax, has been constricted to create the illusion of an extra section. They complete the ruse by waving the front pair of legs to resemble a six legged insect with antennae.

Many other animals also mimic ants, including several other spider families, mantises, bugs, beetles and katydids. The process is called myrmecomorphy. But why mimic ants?

For the ant-mimicking jumping spiders the benefits are twofold. Firstly, they can fool predators. Many ants are distasteful and often bite or sting so insectivores such as lizards and birds often actively avoid eating them. Mimicking harmful or distasteful animals to avoid predation is called Batesian Mimicry, Secondly, many of the ant-mimicking spiders are aggressive mimics. They actually feed on ants, and move freely among the insects they are eating.

The next time you see an ant dashing about erratically with its feelers waving, have a closer look. All may not be as it seems. You just may have encountered one of the many species of Myrmarachne. It takes a keen eye to pick these artful ant-mimics!

Queensland Museum's Find out about... is proudly supported by the Thyne Reid Foundation and the Tim Fairfax Family Foundation.

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