Sex Pranks of the Orchid World

Carl Zimmer's new book excerpted in Discover:

Tangledbank Anne Gaskett, a Cornell University biologist, spends her days crouching quietly next to orchids in Australia. It may seem like an uneventful way to pass the time, but she is actually observing a marvelous act of sexual deception. The flowers are fooling wasps into making love to them.

Male wasps normally seek out females by sniffing for their pheromones, signaling chemicals that they produce. Each species makes a unique pheromone, which means that male wasps rarely end up with the wrong females. But the flowers that Gaskett studies, called tongue orchids, can produce a molecule that precisely mimics the pheromone made by the females of the species Lissopimpla excelsa, commonly known as dupe wasps. Male L. excelsa wasps pick up the scent of the orchids and race to the flowers, expecting to find a mate.

The deception only deepens when the wasp approaches the flower. The pheromone-like compounds are released from a part of the flower that has the coloring of a female dupe wasp. When a male wasp lands on the tongue orchid to investigate, he finds that his body fits snugly against it, just as it would against a female wasp. The dupe wasp is so profoundly fooled that he even extends sexual pincers, called genital claspers, into the flower.

More here.