Unique among hard-shelled creatures is the horseshoe crab, though not really a crab. Actually an evolutionary oddity, this crab has not changed its utterly unfashionable appearance for more than 350 million years, and is actually an arthropod, related more to a spider than a crab.
Every year in late spring the horseshoe crab crawls onto the beaches of the Eastern Shore to lay eggs. Slaughter Beach is an especially exemplary area and is sheltered to enable spawning. The high tides on this Delaware Beach and the coincidence of migrating birds during the full moon in May attract many an enthusiastic birder and curious crab watcher to these sheltered beaches to watch the female crab crawl up to the high water line, usually with one or more male attached by their claws. The female drags them through the sand during the spawning process, laying up to 100,000 eggs in a cluster which will hatch within two to four weeks.
During the trip from the ocean to the tide line in the sand to lay eggs, the female which is larger than the male will occasionally flip on its back, destined to perish unless the tide or a human rescuer flips the hapless lady onto her stomach again.
Volunteers often are found walking the beaches looking for stranded females and gently turning them and place them carefully back into the surf.