Mature horseshoe crabs then repeat what has occurred for years, an annual spring migration to inshore spawning areas. If a horseshoe crab can survive the rigors of spawning, it may live to 18 years of age. Horseshoe crabs are well known for their highly visible mating activities. Spawning in the Chesapeake usually begins in late May when large numbers of adults move onto beaches to mate and lay eggs. The peak in spawning activity usually coincides with the full moon and evening spring tides.
Adults prefer beach areas within bays and coves which are protected from rough water.
Eggs are laid in clusters or nests along the beach, usually between high and low tide. Several nests are made during one beach trip and females will return on successive tides to lay more eggs. Females can produce approximately 88,000 per year. Egg development usually takes about a month and once hatched, larvae usually swim around in the shallow intertidal areas near the beaches where they were spawned until they settle to the bottom and molt. Juvenile horseshoe crabs spend their first and second summer on the intertidal flats and then begin moving offshore.