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Female impersonators of the insect world
By Kate Dalke

For male ants looking for love without a fight, smelling like a queen is just the ticket. They smell like females to avoid attacks by other more aggressive males, and, despite their feminine aura, still mate successfully with virgin queens in the nest.

Fight between aggressive wingless males.

This is a rare example of 'chemical mimicry' within a species—males take on the odor of females in order to protect themselves without ruining their chances to mate. Scientists made the discovery in Cardiocondyla obscurior, a tropical ant whose males come in two varieties: aggressive wingless and docile winged.

The researchers found that young, docile males produce a chemical odor similar to virgin queens. The chemicals, called hydrocarbons, stick to the ants' cuticles, allowing the insects to recognize each other's smell.

The genes that may contribute to chemical mimicry are not known, says Sylvia Cremer, of the University of Regensburg in Germany, who led the study. Docile males must have had enormous selective pressure to survive their first few days of life, she adds.

Female mimicry has been seen in other creatures such as male rove beetles and garter snakes. But in these cases, "males pay for avoiding competition with 'high-quality' males by suffering low mating success with females," the researchers write in Nature.

For the docile Cardiocondyla males, female mimicry is a win-win situation. They avoid fights and copulate with females despite their ladylike scent.

Aggressive wingless male with elongated mandibles for fighting (left) and docile winged male with protective chemical cloak (right).

Smelling like a female doesn't come without its annoyances, however. The aggressive males, confused by the scent, try to copulate with docile males. In fact, this was the first clue for the researchers that there was some sort of chemical deception going on in the nest.

"The nests are very dark, and the [aggressive] males don't have very large eyes. Here, chemical communication is the main attraction," says Cremer.

The researchers discovered that the docile males lose their ladylike scent as they age. Older males that emerged from the nest have their own distinct smell.

Cremer plans to study invasive ant species in Europe and will investigate how smell affects aggression between colonies.

See related GNN article
»Aggression studies reveal the existence of ant supercolonies

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Cremer, S. et al. Male ants disguised by the queen's bouquet. Nature 419 897 (October 31, 2002).

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