Thoe puella
A rare little find off Grand Cayman, this small crab turns up in warm 25-31C reef water year-round.
A small, compact crab with a rounded, somewhat triangular shell and a reddish to mottled scarlet colouring that helps it blend into reef rubble and coral debris. Its legs are relatively short and it tends to stay low and tucked against structure rather than out in the open. Look for the shell shape and colour together rather than any single bold marking, since at this size it is easy to swim straight past.
Divers who spot this crab usually find it sitting still against rubble or reef crevices rather than moving across open sand, relying on its colour and small size to stay unnoticed. It does not react much to divers and is easy to miss unless you are scanning close to the substrate. Given how rarely it is reported even at known sites, most sightings seem to come from divers deliberately searching nooks and rubble patches rather than casual mid-water cruising.
It is currently only confirmed from two dive sites worldwide, both in Grand Cayman, making it one of the rarer crab sightings a diver could log there.
No clear seasonal pattern shows up in the sighting data, and the warm 25.2 to 31.2C water it's found in stays fairly stable year-round in Cayman, so there's no particular month to target over another.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Logged sightings currently come from Grand Cayman in the Cayman Islands, making it the only confirmed region for this crab. It is not a species to plan a whole trip around, but Cayman divers doing slower reef and rubble-zone dives have the best documented shot at it.
Mapping where Scarlet Mime Crab is logged…
The only confirmed sightings are from Grand Cayman in the Cayman Islands. It has not been documented elsewhere in diver or citizen-science records so far.
There's no detected season for this crab, and it lives in consistently warm water between about 25 and 31C, so sightings appear possible year-round rather than tied to a particular month.
Look for a small, rounded crab with a reddish, mottled shell tucked tight against rubble or reef crevices. It stays low and still, so slow, close scanning of the substrate is key to spotting one.
Exact size data isn't available, but like most mithracid crabs it's a small species, easily overlooked against reef rubble unless you're looking closely.
Yes, it's logged as rare even at the two known sites where it has been recorded, both in Grand Cayman. It's considered a real find rather than a reliable sighting.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Sally Lightfoot Crab
2,422 sites
