For days, a female lobster squirts urine into the den of her desired mate. Beguiled by the scent, he lets her move in. Foreplay lasts for days: stroking each other with antennae and feet, which are covered with scent receptors.
Once she’s convinced that he’ll protect her, a female disrobes: slowly shedding her hard shell and the pouch where she had banked sperm from her last mate. Molting leaves her vulnerable, so he stands guard for the half hour it takes for her new soft shell to harden. Then, supported by his hind claws, he suspends himself above her, and lifts her to face him, cradling her in his legs.
Her new shell has a new sperm pouch, into which he thrusts a packet of sperm using his gonopods: the specialized appendages that male lobsters use to transfer sperm. The deed is done.
After she departs, he will welcome another female. Meanwhile, the departed female will use her sperm packet to fertilize thousands of eggs, which she will carry under her tail for a year until the larvae hatch.
Lobsters only mate when the water’s cold. In warm water, lobsters instead put their energy into growing. With constantly warm water, lobsters simply stop mating.
If it’s steadily too warm, they just won’t produce. No eggs. No sperm. No lobsters. ~ American marine biologist Diane Cowen