---
title: Common Box Crab (Calappa bicornis)
scientific_name: Calappa bicornis
common_name: Common Box Crab
taxon: Crabs
published: 2026-08-08T21:11:47.382Z
updated: 2026-08-09T05:47:45.398Z
tags: Common Box Crab, Calappa bicornis, Crabs, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/crustaceans/crabs/common-box-crab
---

# Common Box Crab (*Calappa bicornis*)

## Quick facts

- **Group:** Crabs (*Brachyura*)
- **Size:** up to 7 cm
- **Depth:** 2-40 m
- **Diet:** Durophage
- **Activity:** Nocturnal
- **Rarity:** Uncommon
- **Habitat:** Sand and silty bottoms, buried by day
- **Reproduction:** Brooder, Gonochoric

## How to recognise it

- domed shell with winged rear corners, drawn out into points
- claws fold flat across the front like shutters
- buried in sand with only the eyes exposed
- width up to 7 cm

A box crab with a domed shell whose rear corners are drawn out into two points, and claws so shaped that they fold flat across the front and close the animal into a smooth box - the posture that names the group and leaves no soft part exposed. Width reaches about 7 cm (3 in).

It spends the day buried in sand with only the eyes showing and hunts at night, and the right claw carries a tooth used as a tin-opener: the crab grips a snail shell and peels the whorls away in a spiral until the animal inside can be reached. Empty shells cut in that pattern are a reliable sign one is working the area even when the crab itself is out of sight. Sandy bottoms beside reef are the place to look, on a night dive, at the base of the slope where shells accumulate.

## Also known as

- **English:** Two-horn Box Crab
- **Portuguese:** Caranguejo-cofre-crioulo
- **Japanese:** フタバカラッパ
- **Russian:** Краб-коробочка двурогий

## Scientific synonyms

- *Calappa gallus var. bicornis* Miers, 1884

## Range

Indian Ocean, Seychelles

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*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/crustaceans/crabs/common-box-crab)*
*Updated: August 9, 2026*