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Wasps aren鈥檛 known for their swimming abilities, but one recently identified species is quite at home in the water. Godzilla wasps (Microgaster godzilla) plunge into ponds to hunt aquatic caterpillars, before erupting back out of the water in a way reminiscent of the famed Japanese monster鈥檚 emergence from the sea.

Jos茅 Fern谩ndez-Triana at the Canadian National Collection of Insects, Arachnids, and Nematodes in Ottawa worked in collaboration with researchers at Osaka Prefecture and Kobe Universities in Japan, who first found the creatures while studying pond habitats.

The tiny wasps are black with golden legs and are smaller than a grain of rice. They are parasitoids, implanting their eggs inside the bodies of other insects, where they hatch. The larvae go on to eat their living hosts from the inside out. In this case, the wasps鈥� hosts were aquatic caterpillars of the Elophila turbata moth, which live near the water鈥檚 surface in a case fashioned from plant fragments.

The team brought caterpillar hosts back into the lab and reared their parasitoid wasps, studying how the adults caught their targets. In the aquarium, as in a natural setting, the insects walked along floating plants on the water鈥檚 surface as they searched for caterpillars. Sometimes they would wait for caterpillars to poke out of their cases and then jab them with their egg-laying ovipositors.

Other times, the wasps would dive underwater for several seconds, clinging to the bottom using big hooks on their feet so they could grab the cases from underneath and yank stubborn caterpillars free.

On one occasion, a wasp was underwater for about 14 seconds while it coaxed a caterpillar out of its protective case. 鈥淚 tip my hat to that,鈥� says Fern谩ndez-Triana, as such an athletic feat is risky for the air-breathing wasps.

When he compared the wasps鈥� physical features and DNA with those of close relatives, he found that the insects were an undescribed species.

M. godzilla is one of only a handful of known aquatic parasitoid wasps, and the only member of its caterpillar-hunting subfamily to dive underwater.

In a sense, the targeting of aquatic caterpillars by wasps isn鈥檛 surprising because most insect species are hosts to at least one species of parasitoid wasp, says Paul Ode at Colorado State University, who wasn鈥檛 involved with the study.

Ode is curious about how the wasps are finding their hosts from the surface. He says it may be that the wasps are sniffing them out, or that vibrations in the water may betray the caterpillars鈥� locations.