DELAWARE BAY, Delaware (Storyful/KFOR) – Wildlife officials say horseshoe crabs spawn in mass quantities under a full moon or a new moon during May and June in Delaware Bay – home of the world’s largest concentration of horseshoe crabs.

Officials with Delaware Seashore State Park captured video of the June 14th phenomenon, posting on Facebook, “What a beautiful evening last night for our full moon horseshoe crab walk!”

Delaware Division of Fish and Wildlife provides tips for crab viewers.