crabs text index | photo index
Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans
Box crabs
Family Calappidae
updated Dec 2019
Where seen? Box crabs are sometimes seen on some of our shores.

Features: Body width 8-10cm. The crab does look rather box-like with a semi-circular body and wing-like extensions on the sides and back that cover part of the walking legs. It holds its pincers in front of its body to form a boxy shape. So it is sometimes also called the Shame-face crab as it appears to be covering its face in shame.

What does it eat? The pincers of box crabs are specialised for cracking open snail shells. The snail is gripped in the left pincer which has pointed claws. With the right pincer, which is stronger, the crab cuts pieces of the shell from the shell opening. Once the gap is big enough, the crab can enjoy its snail meal.

Status and threats: Our box crabs are listed as 'Vulnerable' on the Red List of threatened animals of Singapore.
Like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution.  Trampling by careless visitors also have an impact on local populations.

Pulau Hantu, Apr 10


Two different kinds of pincers.

Some Box crabs on Singapore shores

Reef box crab

Spotted box crab

Family Calappidae recorded for Singapore
from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore
in red are those listed among the threatened animals of Singapore from Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore.

  Family Calappidae
  Calappa lophos (VU: Vulnerable)
Calappa hepatica (Reef box crab) (VU: Vulnerable)
Calappa philargius (Spotted box crab) (VU: Vulnerable)


  • Ng, Peter K. L. and Daniele Guinot and Peter J. F. Davie, 2008. Systema Brachyurorum: Part 1. An annotated checklist of extant Brachyuran crabs of the world. The Raffles Bulletin of Zoology. Supplement No. 17, 31 Jan 2008. 286 pp.
  • Lim, S., P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life and Times of Labrador Beach. Division of Biology, School of Science, Nanyang Technological University & Department of Zoology, the National University of Singapore. 160 pp.
  • Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore. Nature Society (Singapore). 285 pp.
  • Jones Diana S. and Gary J. Morgan, 2002. A Field Guide to Crustaceans of Australian Waters. Reed New Holland. 224 pp.
links | references | about | email Ria
Spot errors? Have a question? Want to share your sightings? email Ria I'll be glad to hear from you!
wildfactsheets website©ria tan 2008