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Species: Helmablatta louisrothi

Habitat: Lava caves in Vietnam

It’s one of the weirdest-looking cockroaches ever known, sporting a huge head with a helmet and extra-long legs. “It looks like a forthcoming Star Wars personality,” says Peter Vršanský, who has described the new species.

Vršanský and his colleagues found it in the Tan Phu cave, part of a lava-tube cave system running a few metres below the soil surface under a forest in southern Vietnam.

Rather than feeding on bat guano like many other cave cockroaches, the new species instead graze on bacteria and fungi. Particles that look like fungal spores were found in the gut of the new species.

Guano aside, it may still make use of the bats. Riding on bats could be a useful mode of dispersal for these cave dwellers – and this may partly explain some of their weird appearance.

“Morphologically, it is apparently the most bizarre cockroach which has ever lived that we know of,” says Vršanský, who is at the Slovak Academy of Sciences in Bratislava. It is tiny, at just 3 millimetres long, and largely translucent with reduced eyes.

“The most interesting features are hidden at the back,” says Vršanský. One of these is the huge helmet that gives it a halo-like appearance when viewed from below. Others are a big hook and a “nipper” further down its back.

These features may help the cockroach attach to a female for reproduction, but they may also help the creatures hook together to piggyback on bats to new caves. In evolutionary terms, there’s little point being the only cockroach in a new cave: much better to bring along a mate.

Pheromone lure

On its back, the cockroach also sports modified curled wings that are no longer used for flying, and a specialised “tergal gland” that produces secretions as a kind of nuptial gift for females.

Such gifts are used by the males of many cockroach species to gain the favour of females. But this one does things differently.

“This new species lacks the typical fat nitrogen-rich body found in other cockroaches, so it cannot make a really valuable nutritious morsel for the females,” Vršanský says. “Instead, it lures the female with scented promises and then grabs her tightly.”

The large specialised gland on the male’s back releases pheromones that attract a mate. Once close enough, he captures the curious female with his specialised body parts, holding her down with the helmet and hooked nipper.

Vršanský describes a possible mating scenario based on the traits of the new species: “First, the four modified wings hold the female’s head, and place the head under the helmet-like structure. Then the nipper, a sort of pliers, grabs onto the female’s abdomen and the hook fixes on the genitalia. Together, these structures effectively capture the female and secure mating.”

The lava tubes in which this cockroach was found are fairly young geologically, so the team thinks the creature evolved its weird looks and lifestyle less than 2 million years ago.

Journal reference: Zootaxa, DOI:

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