Compound Eye

Compound Eye

The many facets of science photography

An Enemy in the Ranks


About face: the false ant on the rear of the ant-mimic crab spider Amyciaea albomaculata.

Imagine, for a moment, the horror if we humans were stalked by a common predator that hid itself in the open by looking...just like us. A humanoid patrolling the streets like a bloodthirsty mannequin, picking off pedestrians that venture too close. Fortunately for us, this sobering thought is only a grim fantasy.

Australian weaver ants, however, routinely face just such a nightmare predator. Several species, in fact. Weaver ants (Oecophylla smaragdina) contend with a number of ant-like spiders that look similar enough to their favored food to avoid detection by the ant guards. They lurk around the ants' trails, pretending to be ants and grabbing a meal when the opportunity arises.

During my recent travels in tropical Australia I spent a morning observing an ant-mimic crab spider Amyciaea albomaculata. The following photo essay shows the spider at work.

A weaver ant worker pauses to groom herself. Notice that her eyes are about the same size and distance apart as the eyespots on the rear of her predator.

Weaver ants make nests by binding leaves together with silk.

The spider grabs a hapless ant, injects a paralyzing venom, and drags her victim up a vine and away from the ants' busy trail.

The great getaway.

The spider finds a quiet spot away from the ants' trail to inject a slurry of digestive enzymes.

Does this spidey-face remind anyone else of a Studio Ghibli monster?

Once the venom has turned the ant's innards to soup, the spider sucks the mixture up as though it was a little ant slurpee. This photo shows an air bubble forming inside the ant's head as the spider drinks.

A male Amymyciaea I photographed near the female. During my morning's observation she appeared uninterested in his advances and chased him away. He is recognizable as a male by the bulbous sex organs near his mouth.

See also Aphantochilus rogeri, a New World crab spider that attacks turtle ants:

The Ant That Wasn't

The views expressed are those of the author and are not necessarily those of Scientific American.

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