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Last Updated: Friday, 22 July 2005, 12:23 GMT 13:23 UK
Killer caterpillar stalks snails
<i>Hyposmocoma molluscivora</i>, Science
The caterpillar is unique to Hawaii
A team of scientists has discovered a tiny caterpillar in Hawaii that binds snails with silk webbing before devouring them whole.

The caterpillar starts munching at the wide opening of the helpless snail's shell and continues until there is nothing left, Science magazine reports.

The creature is a first because scientists have never before witnessed a caterpillar eating a snail.

The team wants to know why this strange caterpillar lives only in Hawaii.

"Caterpillars and terrestrial snails co-occur widely on all the continents where they are present, but only in Hawaii have caterpillars evolved to hunt snails," Daniel Rubinoff and William Haines, from the University of Hawaii, wrote.

Why Hawaii?

This provides fresh evidence for the importance of isolation in the evolution of novel traits
Dr Rubinoff and Dr Haines, University of Hawaii
The caterpillars of the newly discovered species Hyposmocoma molluscivora are the first to be seen using silk to paralyse their prey.

"Although all caterpillars have silk glands, this predatory caterpillar uses silk in a spider-like fashion to capture and immobilise prey," Dr Rubinoff and Haines wrote.

When it comes across a suitable snail, the juvenile moth will spin a web anchoring the snail's shell to the leaf it is sitting on.

The larva then stretches its body out of its own silk jacket and pursues the retreating snail to the end of its shell, where there is no escape.

<i>Hyposmocoma molluscivora</i>, Science
Scientists want to know why Hawaii has more than its share of strange creatures
Scientists are curious to notice that this unique predatory behaviour seems to occur nowhere else on Earth.

Since the Hawaiian islands are the most remote place in the world, scientists are tempted to conclude that isolation is a key factor in the development of unusual hunting strategies, although it is not quite clear why.

"Specialised predatory behaviour by lepidopteron larvae, an extremely rare phenomenon worldwide, has independently arisen at least twice in Hawaii," Dr Haines and Rubinoff wrote.

"[This] provides fresh evidence for the importance of isolation in the evolution of novel traits."

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