Environment drives fashion sense: lady damselflies aren't just mimicking the male color

Science News, July 19, 2008 by Susan Milius

MINNEAPOLIS -- It's not the sexual harassment. It's the sunshine. That's Idelle Cooper's new take on the evolutionary force driving female Hawaiian damselflies to dress like males. The slim bodies of male Megalagrion calliphya damselflies shine fire-engine red, says Cooper, of Indiana University in Bloomington. Species-wide, half the females have grass-green bodies, but the others sport the brilliant guy-red.

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Such cross-dressing females show up among insects, lizards and birds. And biologists have typically suggested that this male mimicry reduces the relentless pursuit by sex-obsessed males.

These damselflies, though, may be adapting to their habitat rather than avoiding annoying propositions, Cooper reported June 23 in Minneapolis at the Evolution 2008 meeting.

While the males stake out territories on exposed streambeds, females stay in adjacent shrubbery, visiting the males for mating and egg-laying.

In sparse, high-altitude vegetation, Cooper found females in landscapes as sunny and exposed as male territories. There, both sexes are bright red. Her work also suggests that red pigments defuse potentially damaging free radicals in tissues exposed to sun.

The finding could lead to closer looks at other male-colored females, says Laura Sirot of Cornell University.