Male pond skaters use scare tactics to make females have sex with them, a study shows.
The animals play on a female fear of predators to threaten unwilling partners into sexual submission, the journal Nature Communications reports.
Pond skaters are tiny animals about 1cm to 2cm long.
They are best known for their long legs and amazing ability to skate on the surface of water at speeds of more than a metre per second.
The surprising sexual habits of the humble pond skater have been uncovered by Professors Chang Han and Piotr Jablonski of Seoul National University, South Korea.
Female pond skaters generally call the shots in sexual encounters because they have a "chastity shield" that covers their genitals. This means that males can only successfully mate when a female consents.
However, Professors Han and Jablonski observed that males cause the water's surface to vibrate during courtship rituals, creating tiny ripples. These ripples attract predatory fish lurking beneath.
The male persists in this seemingly reckless action until a female "consents" to sex. The implication is that the male pond skaters use scare tactics to bully females into sexual submission, playing on their fear of being eaten by predators.
Professor Jablonski said that this study provided crucial new evidence concerning "the antagonistic co-evolution between sexes".
Females are much more vulnerable to predators during courtship because the male is positioned on the back of the female, further away from the water's surface.
The scientists found that females succumbed to male advances much more quickly if they had previously experienced a predator attack.
Dr Mark Brown, an expert on insect behavour at Royal Holloway, University of London said: "This is a very exciting discovery. We've studied the sexual habits of pond skaters for decades, but this is totally unexpected."
Last year, the same research team interpreted the male's vibrations as a courtship serenade.
The new findings paint a rather different picture. They show that coercion, not romance, marks the sex life of the humble pond skater.