Like the Atlantic moon snail, the lightning whelk, the knobbed whelk, and the channeled whelk, they feed on clams; they also include worms and other invertebrates in their diet. The horseshoe crab places a clam near its mouth in the center of its underside where its legs are attached and grinds and crushes with the burr-like sections of the legs.

The first four of the five pairs of legs are used for walking, while the last pair, located near the gills, have leaf-like flaps that are used for pushing. (The small pincers on the last pair are also used for cleaning the gills in the abdomen.) Males can be distinguished by the first pair of legs which are heavier than those of the female.

The spike-like tail serves as a rudder, and, if the crab is flipped upside down, it may bend its abdomen at the point where it joins the main shell (carapace) and dig into the sand with the tail to support itself while it turns over.

The horseshoe crab has two pairs of eyes. The first pair is compound, and the second pair, located in the middle of the top front side is simple.

Often you'll find slipper shells attached to the underside of the crab.

In the early summer, the female comes ashore to lay eggs - followed by one or more males (sometimes the first will hitch a ride on her spike, and other males will latch on to him forming a chain). She lays the eggs in pits in the sand (200-300 per pit) near the high-water mark where they are fertilized by the males.

These creatures have not changed much in the last 350 to 400 million years.

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