Calcinus laurentae
Small red-legged hermit crab logged across Hawaii's reefs in water from 22 to 28C, year-round but easy to miss.
Small hermit crab living in a scavenged snail shell, identified mainly by the bright red or reddish-orange banding on its walking legs. The body itself is largely hidden inside the borrowed shell, so divers key on those red legs poking out along with pale eyestalks. Look closely among rubble and coral crevices rather than out in the open, as it stays low and tucked in.
Spotted tucked into rocky crevices and rubble patches, usually moving slowly across the reef floor or hunkered inside its shell during the day. Like other hermit crabs it is more of a scavenger than a hunter, picking over algae and detritus on the substrate, and it will withdraw fully into its shell if a diver's light or hand gets too close. Uncommon at every site it has been logged, so it takes a slow, close look at the reef floor rather than open-water scanning.
As it grows it has to abandon its shell for a bigger one, so divers sometimes spot several individuals sizing up the same empty shell at once, a behaviour typical of hermit crabs generally.
Sightings show no clear season, and with water logged between 22.4 and 28.4C it appears to stay active on Hawaiian reefs all year. Treat it as a year-round find rather than something tied to a particular month.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Every logged sighting of this crab comes from Hawaii, making it a Hawaii-specific find rather than a wider Pacific species from the current data. Divers have picked it out across eight different sites there, so reef and rubble areas around the main Hawaiian islands are the place to look.
Mapping where Redleg Calcinus is logged…
All recorded sightings are from Hawaii, spread across several dive sites there. It has not been logged elsewhere, so Hawaiian reefs are currently the only known place to find it.
There is no detected season for this crab, and it tolerates a wide range of warm water from about 22 to 28C. That points to a year-round presence on Hawaiian reefs rather than a specific month to plan around.
Look for a small hermit crab tucked into a scavenged snail shell with distinct red or reddish-orange banding on its legs. It stays low in crevices and rubble, so a slow, close search of the reef floor works better than scanning open water.
Exact size data is not available, but like most Calcinus hermit crabs it is a small species, easily overlooked among rubble unless you are looking closely.
No, this is a harmless small hermit crab with no risk to divers. It will simply retreat into its shell if disturbed.
Like other hermit crabs, it does not grow its own shell but has to keep upgrading to bigger abandoned snail shells as it grows, sometimes competing with neighbours for the best fit.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Sally Lightfoot Crab
2,422 sites
