Vampire Moth Discovered -- Evolution at Work

Some researchers, she noted, hypothesize that blood-feeding in insects and animals evolved from behaviors such as feeding on tears, dung, and pus-filled wounds.

"We see a progression from nectar feeding and licking or lapping at fruit juices to different kinds of piercing behaviors of fruits and then finally culminating in this skin piercing and blood-feeding," she said.

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Chris Nice, a biologist who studies butterfly evolution at Texas State University in San Marcos, said few butterfly and moth species are equipped with the hook-and-barb-lined tongues needed to pierce fruit.

"The fruit-piercing stage in the first place sets the stage, in a morphological sense, for further transitions into, in this case, the blood-feeding," he said.

Nice added that genetic research such as Zaspel's is the only way to test ideas on how certain behaviors evolve.

Sexual Gift?

The next question is why this Russian population of C. thalictri appears to have evolved blood-feeding behavior, Zaspel said.

Only male moths exhibit blood-feeding, she noted, raising the possibility that as in some species of butterflies and other moths, the Russian moths do it to pass on salt to females during copulation.

"There is no evidence it prolongs the life of the male, or anything like that," she said. "So we suspect that it is probably going to the female."

The sexual gift, she said, would provide a nutritional boost to young larvae that feed on leaf-rich, but sodium-poor, diets.

If salt is otherwise limited in the environment the sexual gift theory "would make sense," Nice added.

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