SCIENCE LAB SCOUTS

PLAYING POSSUM

They may be ferocious predators, but they know when to be passive.

Antlion Larvae are ferocious : They dig pits in the sand and catch unsuspecting prey, stab it with their sharp mandibles and digest it from the inside out.

But to their own predators, Antlion Larvae are simply little snacks. And a colony's cunning traps, grouped together, are quite visible in the sand.

Rather than muster an active defense, the larvae have weaponized passivity - responding to provocation by lying totally still for unpredictable intervals of time that can range from seconds to over an hour.

Many animals behave similarly when faced with danger. Larger vertebrates, like opossums, may emit bad smells to enhance the illusion that are dead, and thus not tasty.

But for the antlion, the key seems to be, not simulated putridity, but simply absolute stillness.

In a new paper, researchers show how this behavior may give antlions a leg up against impatient predators - and in the process shed new light on the effectiveness of playing dead.

The length of time individual antlions played dead varied considerably.

That could be part of the survival strategy, the researchers concluded. If the downtime of a given antlion larva was predictable, predators could perhaps learn a a pattern of behavior.

But there is no pattern - and more food is nearby - a predator might just move on [Cara Giaimo].