Doug Wechsler / Horseshoe crab (Limulus polyphemus) embryos, Delaware Bay, New Jersey, USA, June.

Sean Crane / Horseshoe Crab (Limulus polyphemus) group spawning at high tide at sunset, Cape May, New Jersey

Sean Crane / Horseshoe Crab (Limulus polyphemus) group spawning at high tide at sunset, Cape May, New Jersey

Steve Nicholls / Horseshoe crabs (Limulus polyphemus) spawning at low tide, Slaughter Beach, Delaware, USA, May

Juergen Freund / Horsehoe crab (Tachypleus gigas) swimming on its back with gills creating the propulsion, Palawan, Philippines. Did you know? Horseshoe crabs are more closely related to spiders than crabs.

Juergen Freund / Horsehoe crab (Tachypleus gigas) underside, Palawan, Philippines

Fred Bavendam / Horseshoe Crab (Limulus polyphemus) group crawling ashore on the high tides of spring to lay their eggs in Delaware Bay's sandy beaches, New Jersey

Fred Bavendam / Horseshoe Crab (Limulus polyphemus) group crawling ashore on the high tides of spring to lay their eggs in Delaware Bay's sandy beaches, New Jersey

Fred Bavendam / Horseshoe Crab (Limulus polyphemus) eggs almost ready to hatch after two weeks incubation in the warm sands of Cape Anne, Massachusetts

Piotr Naskrecki / Horseshoe Crab (Limulus polyphemus) gathering on beach to lay eggs, seen under UV light, Delaware National Estuarine Research Reserve, Delaware

Magnus Lundgren / Wild Wonders of China / Staff from Ocean Park Conservation Fund, OPCF, and students visit Ha Pak Nai to see the juvenile Chinese horseshoe crabs, (Tachypleus tridentatus) Yuen Long District, New territories, Hong Kong, China...

Magnus Lundgren / Wild Wonders of China / Staff from Ocean Park Conservation Fund, OPCF, and students visit Ha Pak Nai to see the juvenile chinese horseshoe crabs (Tachypleus tridentatus) in a mudflats, Yuen Long District, Hong Kong, China.