[2][3][4][5][6] They are fairly large to large crabs that typically are reddish in color and spiny, although the size of these spines varies depending on species (from long in species like N. grimaldii to very short in species like N. flindersi, and tending to be more pronounced in small than in large individuals).

[9] They are occasionally the victims of parasitic snailfish of the genus Careproctus, which lay their egg mass in the gill chamber of the crab, forming a mobile "home" until they hatch.

[4] Conversely, some juvenile Neolithodes have a commensal relationship with Scotoplanes sea cucumbers.

To protect itself from large predators, the young crab hides under the sea cucumber.

[10] The word Neolithodes derives from the Greek neo, meaning new, and Lithodes, a closely related genus of king crab.