July 24, 2003 — A newly discovered Australian river bug offers food to her male partner during their four-day sex session, a "nuptial gift" that biologists said is extraordinary in the animal kingdom.
The female Zeus beetle, a semi-aquatic insect known by its Latin name of Phoreticovelia disparate, exudes tasty secretions from glands on her back on which the male partner feasts during their lengthy coitus.
Nor is it just a light snack, said the Swedish-Australian experts who have delved into the torrid lives of these creatures.
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A typical male consumes daily secretions that are equivalent to several percent of his body weight — rather like polishing off a pizza, a bottle of champagne and a box of chocolates between bouts of lovemaking.
The female's gift is highly unusual in evolutionary terms.
Across the animal world, it is traditionally the male who brings food offerings to the female as part of the courtship ritual or during mating.
The theory behind this is that "nuptial gifts" make evolutionary sense: by making the female stronger and healthier with the food, the male is investing in his unborn offspring.
But this argument is unlikely to hold true in the case of female gifts, the authors said.
In the case of the Zeus beetle, the food may be a simple act of survival — to prevent the female from being gobbled up by the starving male after sex.
"Our results indicate that female gift giving is not necessary to ensure a regular sperm supply," the authors said. "Instead, it may have evolved to reduce costs imposed by males, in the form of cannibalism, kleptoparasitism and other forms of interference."
If so, the findings are remarkably appropriate. The beetles are named after the Greek god Zeus, who consumed his first wife, Metis.
The study, published on Thursday in the British weekly science journal Nature, was led by Göran Arnqvist of the Department of Animal Ecology at Sweden's University of Uppsala.
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