Ovalipes ocellatus

The carapace of O. ocellatus is slightly wider than long, at 8.9 centimetres (3.5 in) wide,^[6] and 7.5 cm (3.0 in) long.^[9] The carapace is yellow-grey^[9] or light purplish,^[6] with "leopardlike clusters of purple dots".^[9] It exhibits a limited iridescence as a form of signalling.^[10]

Ovalipes ocellatus is commonly known as the lady crab,^[a] oscellated crab,^[b] or calico crab.^[6] It was first described in 1799 by naturalist Johann Friedrich Wilhelm Herbst, who placed it into the genus Cancer.^[1][2] In 1898, carcinologist Mary Jane Rathbun moved the species to her new genus Ovalipes.^[11] O. ocellatus is part of a distinct group of Ovalipes which also includes O. floridanus, O. iridescens, O. molleri, and O. stephensoni.^[12][10][d] O. ocellatus is almost identical to O. floridanus, which lives in the Gulf of Mexico, but can be separated from the sympatric O. stephensoni by purple spots which O. stephensoni lacks.^[9] The following cladogram based on morphology shows the relationship between O. catharus and the other extant species of Ovalipes:^[10][e]

The distribution of Ovalipes ocellatus extends along North America's Atlantic coast from Canada to Georgia.^[9] O. ocellatus is "probably the only Ovalipes species common north of Virginia", being replaced by Ovalipes stephensoni to the south.^[14]

The diet of Ovalipes ocellatus consists predominantly of bivalves, crustaceans including other crabs, polychaetes, cephalopods, and gastropods.^[15][16] It rarely feeds on fish.^[15]

Ovalipes ocellatus has five zoeal (larval) stages, lasting a total of 18 days at 25 °C (77 °F) and a salinity of 30‰, and 26 days at 20 °C (68 °F) and 30‰.^[17]

Ovalipes ocellatus is nocturnal and often buries itself in the sand.^[6][9] It has been described as "vicious" and "the crab most likely to pinch a wader's toes".^[9]