Description:

Carapace markedly convex regions undefined. Surface minutely squamose anteriorly; posteriorly with minutely beaded transverse lines, increasing in length 
laterally, longest line running parallel to posterior margin.

Colour. Two colour morphs are known: one uniform tan and the other speckled with numerous red to maroon spots but as far as is known, only the uniformly 
coloured beige or light brown form is present in the Indian Ocean.

Maturity: Unknown. Max length : 13.0 cm CW. Largest Calappa species in the Indo-West Pacific.
 

Essentially a coral-reef species, occurring in sub-littoral sandy areas between coral heads (depth 10 -50 m). Active during the night hours, and is able, 
when threatened, to swiftly burrow beneath the sand. It feeds mainly on molluscs such as clams, steadying them with its legs and then, using its pincers, 
either prising the valves apart or breaking them.

This species is not protected or subject to fishery regulations. It is often caught in benthic fish traps but is usually released. 

Galil, B.S. (1997). Crustacea Decapoda: A revision of the Indo-Pacific species of the genus Calappa Weber, 1795 (Calappidae) In: A. CROSNIER (ed.). 
Résultats des Campagnes MUSORSTOM, Volume 18. Mém. Mtis. natn. Hist, nat., 176: 271-335. Paris ISBN 2-85653-51 1-9. 
Palomares, M.L.D. Pauly, D. (Eds). (2023). SeaLifeBase. www.sealifebase.org. Calappa calappa. https://www.sealifebase.se/summary/Calappa-calappa.html# (20/08/23). 
Ng, P.K.L.(2002). The Box and Moon crabs of Thailand, with description of a new species of Calappa (Crustacea: Brachyura: Calappidae: Matutidae). Phuket 
Marine Biological Center Special Publication 23(2): 341–360 (2002).
 

Nevill, J.E.G. & Banane, K. (2023). Calappa calappa, Giant box crab. Seychelles Seatizens. www.seatizens.sc. https://seatizens.sc/invertebrates/calappa-calappa-linnaeus-1758/