Many parasites have developed mechanisms that suppress their hosts' ability to fight them off or even change their behavior in favor of the parasite.

"We found the opposite is true with tiger moth caterpillars and their parasites," said UA Regents' Professor Emerita Elizabeth Bernays.

Bernays discovered the previously unknown phenomenon when she studied tiger moth caterpillars infected with parasitic fly larvae. The presence of the parasites alters their hosts' taste organs. As a result, the caterpillars prefer to consume plants containing chemicals toxic to the parasites.

Bernays, who is in the department of entomology at UA's College of Agriculture and Life Sciences and in the Division of Neurobiology at UA's Arizona Research Laboratories, did the research with Michael Singer, a former doctoral student of hers who is now an assistant professor in the department of biology at Wesleyan University in Middletown, Conn.

"It is a new and surprising kind of interaction between organisms," said Bernays. "When parasites change the behavior of their hosts, it's usually to their advantage."

The chemical war starts when parasitic flies of the tachinid family seek out their victims, the caterpillars of two species of tiger moth, Grammia geneura and Estigmene acrea. The flies lay their eggs on the outer surface (cuticle) of the caterpillar. As soon as the larvae hatch they bore through the cuticle and squeeze inside the caterpillar's body. Inside they feast on the caterpillar's tissue, using it as an ever-fresh live supply of food. When the fly larvae have eventually consumed and killed their host, they pupate and develop into adult flies.

But in the case of the tiger moth, co-evolution between parasite and host has resulted in an arms race involving ch
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Contact: Daniel Stolte
stolte@email.arizona.edu
520-626-4407
University of Arizona
28-Jul-2005