Male diving beetles need fancy footwork to catch a mate. Females in the aquatic beetle family Dytiscidae thrash around to dislodge pursuing suitors, requiring males to use adhesive hairlike structures on their feet to mount them. Scientists believe this chaotic copulation sparked an evolutionary arms race where some male diving beetles evolved circular suckers on their feet in place of the grooved spatula-shaped structures more commonly found on other beetles. To find out whether the suckers provide a tighter grip, a research team removed legs from sedated male diving beetles and measured the force required to pry the adhesive structures from smooth surfaces. The circular suckers withstood seven times more horizontal force than the primitive spatula-shaped structures and offered stronger long-term underwater adhesion, the team reports online today in the Journal of the Royal Society Interface. The researchers believe both structures could inspire improved designs for underwater attachment mechanisms used by scuba divers and maritime salvagers.