ITHACA, N.Y. -- Like eccentric street people who deter muggers by acting crazily, one crafty beetle has developed an equally outrageous defense: Larvae of the tortoise beetle species Hemisphaerota cyanea cover themselves with their own feces, persuading most predators to pass them by, Cornell University biologists have discovered.
But at least one kind of one predator is not repulsed by beetle feces, Thomas Eisner and Maria Eisner report in the March 14 issue of Proceedings of the National Academy of Sciences (Vol. 97, pp. 2632-2646). The reason for the breakdown in a nearly perfect defense remains a mystery.
"You could call this the ultimate in recycling," says Thomas Eisner, Cornell's Jacob Gould Schurman Professor of Chemical Ecology, describing the golden strands of feces extruded from the beetle's hindgut and fashioned into a thatched shield for its otherwise vulnerable body. "Instead of leaving excrement lying around, as most larvae do, this species has developed an overhead sewer system. The thatch grows as the larvae metamorphoses, and for some reason that we don't understand, the fecal shield deters most predators that would gladly eat the naked larva. They won't even try. Maybe they're disgusted by the whole idea."
Then along comes a carabid beetle (Calleida viridipennis), quickly disassembling the thatch shields and feeding on the hapless inhabitants.
The adult H. cyanea is a familiar sight on palmetto fronds of Archbold Biological Station, in the dry scrubland of central Florida where the professor and his wife, a senior research associate in Cornell's Department of Neurobiology and Behavior, conduct research. Called a tortoise beetle because of its turtle-like shape, the iridescent blue adult insect chews trenches through palmetto leaves as it feeds.
Until the Eisners looked closer, however, most casual observers figured the small, golden bits of stuff on palmetto fronds were lifeless. The spots seemed never to move, and th
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Contact: Roger Segelken
hrs2@cornell.edu
607-255-9736
Cornell University News Service
26-Mar-2000