How the heck do crabs do it? I know everyone, like me, has been wondering because those rigid shells look just like a suit of armour. The trick to it (you knew there’d be a trick) is that once a year, in spring, the entire crab population pretty much announces that it’s going to ‘slip into something more comfortable’ and moults. While all this unseemly crab nudity takes place, the crabs also fan pheromones at one another, the crustacean equivalent of standing next to a red light and hitching up one’s skirt. The part I find really sweet about crab sex is that after vigorous crab shagging, the male will guard the female for a few days so her shell has time to harden before he takes off in search of a new mate. Awwwww.