A post-coital catapult might not sound like the most relaxing pillow talk, but for males of the orb-weaving spider Philoponella prominens, making a speedy exit after mating is a matter of life and death. Researchers have found that these spiders will ping themselves into the ether to avoid becoming lunch for females who would otherwise kill and eat them.
The unusual exit strategy is described in a new paper published in Current Biology, which explores how they use their first pair of legs to launch themselves away from their mates to safety the second they're done. The urgency is perhaps reflected in the phenomenal speeds these spiders reached, estimated to clock up to 88 centimeters per second (34.6 inches per second).
The post-sex gymnastics are facilitated by the spider’s tibia-metatarsus joint which they fold against the female. Once mating is complete, the limbs are released, and hydraulic pressure makes them expand at great speed sending the male flying through the air.
Recording the novel strategy proved to be quite a challenge for the paper’s authors who found that the equipment was struggling to keep up with the catapulting speeds. “We found that mating was always ended by a catapulting, which is so fast that common cameras could not record the details clearly,” said lead author Shichang Zhang of Hubei University, China.
The authors first observed the behavior while studying sexual selection in P. prominens which live in communal groups that can house up to 300 spiders in a single web complex. They then set up cameras to get a closer look and investigated what happened when the males were blocked from catapulting using a fine painting brush.
All males that catapulted after sex survived, representing 152 of the 155 observed successful mating attempts. The three individuals that didn’t catapult were killed. A further 30 that were prevented from catapulting after mating also died, which the researchers say demonstrates this behavior’s role as a way of avoiding sexual cannibalism.
“The most surprising results is that male catapults dodge female’s sexual cannibalism with extraordinary kinetic performance,” Shichang Zhang told IFLScience.
“The initial catapulting speed can achieve 82cm/s, and the body length of the male is only around 3 millimeters [0.12 inches]. Imagine a man with a height of 1.8 meters [5.9 feet] catapults off 530 meters [1,738.85 feet] in one second! That’s what the male spider does.”
Flying off at such speeds with less than a second’s notice might seem like a perilous escape plan, but the male spiders were found to have another trick up their sleeve.
“Males pull silks from their spinnerets when they walk on the webs of females, which are anchored on the web silk of females, so when females attack them, they drop down, hanging by the silk,” Zhang explained.
“It is the ‘safety line’... After catapulting, males will be hanged by the safety lines, so that they would not drop to the ground. Later, they will climb back to females’ webs for further mating, they may also go to other females’ webs to search for mating chances.”
While one might take the departure of a sexual partner at such speeds personally, it’s hard to condemn the male spiders’ actions in the context that if they hang around for the afterglow, they will probably end up dead. The authors hope to next investigate if a correlation exists between the catapulting ability of a male with its reproductive success.
