Einstein Science Reporting for Kids
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21-Jul-2005

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Flesh-eating caterpillar spins deadly silk




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In Hawaiian rainforests, scientists have discovered tiny caterpillars "gluing" snails to leaves with silk webbing and then feasting on snail flesh, leaving nothing but empty shells.

The caterpillars start eating at the wide opening of the paralyzed snail's shell and chomp on the snail's body until there is nothing left.

These caterpillars are small, not as long as a single key on a computer keyboard. The caterpillar bodies are mostly covered by a silk case that looks like a miniature sleeping bag. When it's time for the caterpillar to develop into a moth, this case becomes the cocoon.

These caterpillars, which have black shiny heads and light brown bodies, are the first to be seen eating snails or any other soft-bodied creatures with hard shells.

The snail-snacking caterpillars are also the first caterpillars that scientists have observed using silk to paralyze their prey, similar to the way spiders use silk.

By pinning down their prey to a leaf with silk, the caterpillar prevents the snail from escaping by dropping off the leaf.

Sometimes the caterpillars spin empty snail shells onto their yellow, green and grey casings. The shells probably act as a camouflage that helps the caterpillars hide.

Daniel Rubinoff from the University of Hawaii is part of the team that discovered these caterpillars. He is now trying to understand why these weird animals live in Hawaii but not, as far as scientists can tell, other places on Earth.

Part of the answer to this "Why on Hawaii?" question has to do with the fact that the Hawaiian Islands are the most isolated place on Earth. The next land area is a great distance away. This isolation seems to be important for the development of unusual hunting strategies and other fascinating characteristics, though it's not yet clear why.

The snail-stalking caterpillars join the ranks of ambush predator caterpillars and spiders that stab their prey in flight as unique predators from Hawaii.

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This research appears in the 22 July issue of the journal Science.