The Assassin Bug Wears Its Victims’ Corpses as Armor

Like a real-life version of the Predator—that's barely a half-inch in size—the aptly named assassin bug (Acanthaspis petax) wears the bodies of its victims like trophy armor after liquefying and consuming their innards. Disgusting.

After it's made a kill, the assassin bug—which calls Malaysia home—injects its victim with a special enzyme that dissolves and softens its guts so they can be easily sucked out. And once all that's left is the insect's empty shell, the assassin bug attaches those exoskeletons to its back using a sticky secretion, piling them high to create a thick layer of protective armor that also serves to confuse its enemies.

In 2007, a team of researchers from New Zealand carried out an experiment to test whether the insect’s corpse-carrying strategy truly helped protect it from predation. In the study, they left assassin bugs alone in glass cages with several species of jumping spiders, which are their natural predators. Some of the insects were carrying balls of ant carcasses on their backs (the researchers called these “masked” bugs) while others were left naked. Since the jumping spiders have excellent vision but a poor sense of smell—they hunt by using their acute sense of sight to make a precisely gauged leap and land on their prey—the experiment would indicate if the ant bodies served as visual camouflage or not.

The result: the spiders attacked the naked bugs roughly ten times more often than the masked ones. The researchers even repeated the experiment with dead, preserved assassin bugs, to control for the effects of movement and behavior, and the results remained the same. Carrying that ball of dead ants, it turns out, is a great strategy for the assassin bug to use in trying to survive for its next meal.

The scientists speculate that the large mound of corpses changes the visual form of the insect to the point where the spiders can’t recognize it as prey.

But why do the assassin bugs refrain from using other insects in the same way? The researchers suggest that Acanthaspis petax may actually be relying on the spiders’ inherent reluctance to attack ants. Because ants have a tendency to swarm and may secrete chemical weapons, the spiders don’t typically hunt them.

References:

• wikipeadia: Acanthaspis petax
• Bugs with backpacks deter vision-guided predation by jumping spiders