ancient horseshoe crabs have been around in their present form for
about 250 million years, predating most other life on the planet.
They are found in the western Atlantic from the Gulf of Maine to
the Yucatan. Delaware Bay is home to the largest population in the
Atlantic. Though commonly called crabs, they are really more closely
related to scorpions, ticks and land spiders. They have hard, curved
top shells which make them difficult for predators to overturn and
they can go for up to a year without food. When they do eat, horseshoe
crabs prefer a modest, readily available diet of worms and mollusks.
An adult grows to a shell size of more than two feet, and they have
long, barbed tails which act as rudders for moving through mud.