After males of the orb-weaving spider Philoponella prominens mate with a female, they quickly launch themselves away ( Current Biology). Using a mechanism that hadn’t been described before, the male spiders use a joint in their first pair of legs to immediately undertake a split-second catapult action, flinging themselves away from their partners at impressive speeds clocked at up to 88 centimetres per second (cm/s).
The reason the males catapult themselves is simple: to avoid being eaten by the female in an act of sexual cannibalism. The few males the researchers saw that didn’t catapult were promptly captured, killed, and consumed by their female partners. When the researchers prevented males from catapulting, they met the same fate, says a Cell Press release.
Shichang Zhang of Hubei University in Wuhan and colleagues made this discovery while studying sexual selection in this spider, which lives in communal groups of up to 300 individuals in a web complex with many individual webs within it. Of 155 successful matings, they report that 152 ended with the male catapulting. All those catapulting males survived their sexual encounters.
The three males that didn’t catapult were killed. Another 30 prevented by the researchers from catapulting also got killed and eaten by the female. The researchers say that the findings show clearly that the catapulting behaviour is required to avoid sexual cannibalism.
“Females may use this behaviour to judge the quality of a male during mating,” he adds. “If a male could not perform catapulting, then kill it, and if a male could perform it multiple times, then accept its sperm,” Zhang says.
