Common Rock Crab

The Common Rock Crab (Hemigrapsus edwardsi), is a marine large-eyed crab of the family Grapsidae. It is endemic to the sea coasts of New Zealand although not in the Chatham Islands or the southern islands. This common intertidal crab occurs in a variety of habitat, under boulders, on the rocky reef, and on sand and mud flats.

Its shell grows to around 1.5 inches wide. Coloration is a reddish purple, mottled with dirty white patches, with pale green antennules with dark red spots, but there are two colour types: light and dark. Darker crabs are marked with dark purple, sometimes almost purplish black, and their legs are banded.

Females are in berry from March to August, and they carry up to 26,000 eggs for about 6 weeks, during which time the eggs change colour from light brown to transparent.