The rugged sex life of the bean weevil

When it comes to tough love, no one tops the sex life of the bean weevil

When it comes to tough love, no one tops the sex life of the bean weevil. The male's quaintly named "intromittent organ" is a maceshaped affair covered with spikes. The female so dislikes the business of making babies that she repeatedly kicks her partner to speed things up.

This remarkable carry-on is an indication of a "co-evolutionary arms race" according to researchers Dr Helen S. Crudgington and Dr Mike T. Siva-Jothy of the University of Sheffield, who published their study of the weevil in the journal, Nature.

They describe in grisly detail how these bugs make the earth move. It all apparently comes down to increasing one's reproductive chances.

Bean weevil (Callosobruchus maculatus) males are eager to ensure that the sperm deposited by their intromittent organ remains the only show in town.

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Its evolutionary response has been to develop an organ topped with spines. These are sharp enough to lacerate and cut through the female's genital tract.

Not surprisingly, this so puts off the female weevil that her evolutionary response has been to develop a ferocious kick.

The male retreats but the damage done usually ensures that the female will have no part in any more hanky-panky.

For her part, the female is anxious to mate at least once because she, too, is under a procreative imperative to pass on her genes.

One can only assume that romance doesn't play a big part in the mating games played by the bean weevil. For us the early days include the flowers and champagne, when one's partner can't do enough to please. The weevil doesn't have to deal with such complexities, which at the end of the day must save a bob or two.

Dick Ahlstrom

Dick Ahlstrom

Dick Ahlstrom, a contributor to The Irish Times, is the newspaper's former Science Editor.