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Strange Caterpiller Devours Snails

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Strange Caterpillar Devours Snails

By Rossella Lorenzi, Discovery News

 

 

July 22, 2005 — A bizarre caterpillar has been caught red-handed in Hawaii using its silk in a spiderly fashion to ambush and devour snails. The shells are then left hanging around.

 

Flesh-eating caterpillars are extremely rare, and always prefer to eat other insects — never snails, which are mollusks.

 

"It's kind of like finding a wolf that is diving for clams," said entomologist Daniel Rubinoff of the University of Hawaii.

 

Rubinoff and William Haines published their discovery in the July 22 issue of the journal Science.

 

 

The initial discovery of the snail-eating caterpillars came when Rubinoff placed a new Hawaiian moth caterpillar of the genus Hyposmocoma in a box and offered it algae, lichens and other vegetable food, the traditional fare of caterpillars on the rest of planet Earth. The caterpillars wouldn't touch the stuff, he said.

 

Then, only because he'd been told the caterpillars decorate with snail shells, Rubinoff offered the caterpillar a live snail. To his disbelief, the caterpillar took out right after the snail and made a meal of it. "It just blew me away," said Rubinoff.

 

In fact, Rubinoff's initial disbelief didn't budge until several snail meals later, seen also by other people he abruptly dragged into his lab to witness the unheard-of caterpillar dining preference. He wasn't entirely convinced it was real, he said, until he found four other species of flesh-eating caterpillars on other Hawaiian Islands.

 

The five new species of snail-eating Hyposmocoma caterpillars belong to a rather exclusive dinner club among insects, said Rubinoff. Out of at least 150,000 known species of moths and butterflies in the world, there are only about 200 species that are not vegetarians — just 0.13 percent.

 

More than just being rare in their food preferences, however, the newfound snail eaters are a great example of evolution at work. They show how the few animals that make it to remote, isolated islands can then evolve into new species with novel lifestyles.

 

The Hawaiian Islands are considered among the most remote in the world when it comes to natural access by animals and plants.

 

"It's not isolated for whales or migratory birds, but for most terrestrial organisms the Hawaiian Islands are very, very isolated," said Hawaiian spider expert Rosemary Gillespie of the University of California at Berkeley.

 

As a result, those organisms that reached the first Hawaiian island found a lot of space to grow, and a lot of possibilities for making a living, Gillespie explained.

 

That's why the Hawaiian Islands have one of the highest numbers of local, or endemic, species per square mile on the planet.

 

As for how the caterpillars reached the other islands, they might have followed a pattern seen in other Hawaiian species, Gillespie surmised. Many Hawaiian species appear to have hopped from older islands to younger islands as new volcanic islands in the chain were created.

 

Each hop offered new opportunities to evolve into new species, a concept first observed and explained in the 19th century by none other than Charles Darwin when he described the diverse finches of the Galapagos Islands.

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