July 21, 2005

Hawaiian caterpillars hunt like spiders -report

WASHINGTON (Reuters) - Tiny, snail-eating caterpillars
found in Hawaiian rain forests tie up their prey with sticky
silk and snack on them at leisure, surprised scientists said on

It is the first time that caterpillars that eat snails or
any other mollusk have been found, the researchers write in
Friday's issue of the journal Science.

And while caterpillars of all kinds spin silk to make
cocoons, this is the first time one has been seen to use it as
spiders do to capture prey.

"Although all caterpillars have silk glands, this predatory
caterpillar uses silk in a spiderlike fashion to capture and
immobilize prey," Daniel Rubinoff and William Haines at
University of Hawaii wrote in their report.

The caterpillars of the newly described species,
Hyposmocoma molluscivora, are small -- about a third of an inch
(8 mm) long. Wrapped in their cocoons, they "lumber along"
leaves, Rubinoff and Haines said.

"The caterpillars do not eat plant foliage, even when
starving," they wrote.

Instead, they hunt Tornatellides snails.

When they find one, "they immediately begin to spin silk
webbing attaching the snail shell to the leaf on which it
rests, apparently to prevent the snail from sealing itself
against the leaf or dropping to the ground," the researchers

"The larva (caterpillar) then wedges its case next to or
inside the snail shell and stretches much of its body out of
its silk case, pursuing the retreating snail to the end of the
shell from which there is no escape. We observed 18 attacks by
10 different larvae following this sequence."

Sometimes the caterpillars decorate their silk casings with
empty snail shells, probably as a form of camouflage, the
researchers said.

The caterpillars eventually become small moths.

The researchers say they are surprised by the findings and
note the caterpillars join a range of unusual Hawaiian fauna,
including spiders that impale their prey in flight.

"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," they wrote.