The giant hermit crab, Petrochirus diogenes, is one of the most distinct hermit crab species in Florida. The portion of the body directly behind the eyes, called the anterior shield, is flattened, roughly square in shape, with tufts of hairs called setae scattered across the surface (Williams 1984). The front portion of the shield posterior to the eyestalks is trilobate (forms 3 lobes). The eyestalks are straight with setae above each cornea and along the length of each stalk. Claws are unequal in size (Ruppert & Fox 1988), a characteristic in crabs called heterochely (Bertini & Fransozo 1999). Although claw size varies with sex (see "Reproduction" below), the right claw is dominant and larger in both males and females. The two end segments (chelae) of the claw that together form the pincers, referred to as the 'hand', are roughened with coarse tubercles, or bumps, separated by setae across the surface with a row of spines lining the inner margin.Tubercles are also present on the inner crushing surface of the major chela and the minor chela is slightly concave, forming a spoon shape. The 2nd and 3rd pairs of appendages that serve as the walking legs are hairy underneath with a row of sharp spines down the two end segments, called the dactyl and propodus. The body of P. diogenes is generally red in color (Williams 1984; Ruppert & Fox 1988), with white spots on the carpus (3rd segment from the tip) of the walking legs, and red and white stripes at the base and tips of the antennae and antennules.