Crab or horseshoe crab?
How to tell them apart
Despite its name it is not a crab or even a crustacean: it is a chelicerate, more closely related to spiders, ticks and scorpions.
Quick answers
They differ on 4 of the 8 quick answers: what is it, awake when, kept as a pet, do people eat it.
| Question | Crab | Horseshoe crab |
|---|---|---|
| What is it? differs | Crustacean | Arachnid |
| Carnivore? | Omnivore | Omnivore |
| Dangerous? | No | No |
| Domesticated? | No | No |
| Awake when? differs | Day & night | Night |
| Hibernates? | No | No |
| Kept as a pet? differs | Sometimes | No |
| Do people eat it? differs | Yes | In places |
At a glance
| Question | Crab | Horseshoe crab |
|---|---|---|
| Found in differs | Oceans, Worldwide | Oceans, North America, Asia |
| Habitat differs | Coast, Open ocean, Rivers & lakes | Coast |
| Size | Small | Small |
| Length differs | A few mm (pea crab) to a 4 m leg span (Japanese spider crab) | Up to 79.5 cm with the tail (tri-spine horseshoe crab) |
| Weight differs | – | Largest females up to 4–4.8 kg |
| Legs | 10 | 10 |
| Covered in | Shell | Shell |
| Lives | In groups | In groups |
| Lives for differs | 3–30 years | 20–40 years |
| Can fly | No | No |
| Swims | Yes | Yes |
| Lays eggs | Yes | Yes |
About each
Crab
Armoured crustaceans with the tail tucked under the body, able to run sideways. The crab shape has evolved several separate times, a process called carcinisation, so crabs aren’t one natural group.
Horseshoe crab
Not a crab at all but a relative of spiders and scorpions, little changed for about 250 million years. Four species survive: one on the Atlantic coast of the US and Mexico, and three in South, Southeast and East Asia. It lives on the seabed but can swim, and comes ashore to spawn.
Everything on the horseshoe crab page
Sources
Last reviewed . The answers and notes come from each animal's own page, where every source is listed.
How each answer is decided: How we answer. More look-alikes: Side by side.