Watch this caterpillar fling its beetle attacker t...

Soft, squishy caterpillars might seem like easy prey to a hungry predator, but one species doesn’t give up without a fight. Fully developed caterpillars of the hornworm moth (Langia zenzeroides) use a mix of squeaks, strikes, and vomit to defend themselves from predators, researchers report this month in the Biological Journal of the Linnean Society. Hornworm moth larvae respond aggressively when pecked by vertebrate predators such as birds, but it wasn’t clear whether they reacted toward invertebrate predators in a similar fashion—and whether invertebrates, too, could have played a role in the evolution of caterpillar defenses. So, scientists tested how hornworm moth larvae fared in the presence of caterpillar-hunting insects. Adult ground beetles of the genus Calosoma fit the bill perfectly as they eat a variety of caterpillar species in the wild and take down prey bigger than themselves. But when the beetle approached a hornworm caterpillar, it got attacked and shoved away. And when the beetle tried to bite, the caterpillar launched additional defenses: It squeaked, which is known to startle predators, and threw up on its attacker, possibly as a chemical defense. Most dramatically, two caterpillars grabbed the beetle in their jaws and flung it through the air. One of these even managed to bite off part of the beetle’s right hindleg. All of these strategies paid off: None of the 25 beetles tested was successful in killing a single caterpillar, the team found.