Study: Butterflies choose medicinal plants

ATLANTA, Oct. 11 (UPI) -- Monarch butterflies seem to use medicinal plants to treat their offspring, choosing certain ones to lay their eggs on, a U.S. study shows.

Researchers at Emory University in Atlanta found female butterflies, known for long-distance migration from the United States to Mexico each year, seem to prefer to lay eggs on a species of milkweed that is toxic to a parasite infecting some butterflies that can then infect their larvae and caterpillars, a university release said Monday.

Females infected with the parasites preferred to lay eggs on a toxic species of milkweed, rather than a non-toxic species, while uninfected female monarchs showed no preference, the study found.

"We have shown that some species of milkweed, the larva's food plants, can reduce parasite infection in the monarchs," Jaap de Roode, the evolutionary biologist who led the study, said. "And we have also found that infected female butterflies prefer to lay their eggs on plants that will make their offspring less sick, suggesting that monarchs have evolved the ability to medicate their offspring."

"The results are also exciting because the behavior is trans-generational," Thierry Lefevre, a postdoctoral fellow in de Roode's lab, said. "While the mother is expressing the behavior, only her offspring benefit."

The findings may have implications for human health, University of Michigan chemical ecologist Mark Hunter, who collaborated on the research, says.

"When I walk around outside, I think of the plants I see as a great, green pharmacy," Hunter says. "Studying organisms engaged in self-medication gives us a clue as to what compounds might be worth investigating for their potential as human medicines."