Snow crabs are spider-like in shape, with a flat, round carapace (shell) and long, slender legs. Their colour changes as they age. Soon after they moult, snow crabs will be reddish on top and white on the bottom. As they get older, this red will fade to a duller olive shade and their underside will become yellowish. Snow crabs can grow to a maximum carapace width of about 15 centimetres, with males growing more than twice as large as females (females are not harvested commercially for this reason). They have a maximum life span of 12-13 years.