Argus hermit (Calcinus argus)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Arthropoda · Class: Malacostraca · Order: Decapoda · Family: Diogenidae · Genus: Calcinus.

Accepted name: Calcinus argus · Authority: Wooster, 1984 · Taxonomic status: accepted · AphiaID: 367432.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=367432 (CC BY 4.0). Accessed 2026-09-25.

Biology and life history (SeaLifeBase)

Measured values published by SeaLifeBase for Calcinus argus. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Habitat zone: reef-associated.

Source: SeaLifeBase species summary (SpecCode 21021) — https://www.sealifebase.se/summary/Calcinus-argus.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.

Distribution and occurrence records (GBIF)

69 georeferenced occurrence records for Calcinus argus are published through GBIF from 8 countries or marine areas. The map above plots 14 distinct locations from a sample of 69 records, omitting 5 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: United States of America (40); Réunion (19); Northern Mariana Islands (4); New Caledonia (2); Cocos (Keeling) Islands (1); Guam (1); French Polynesia (1); South Africa (1).

Marine regions with a valid WoRMS distribution record: Réunion Exclusive Economic Zone; New Caledonian Exclusive Economic Zone.

Source: GBIF Occurrence Search (taxonKey 2224432) — https://www.gbif.org/occurrence/search?taxon_key=2224432&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=367432 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-25.

Description and natural history (Wikipedia)

Calcinus argus is characterized by their unique colorization compared to other Calcinus species found in the same region. This organism features a unique, distinctly sized and spaced white spots across their three pereopods (walking legs) against a maroon shell. They typically have longer, slender, eye stalks, along with a less rounded carapace.

Calcinus argus has the segmented head, thorax, and abdomen, of the phylum Arthropoda. This organism has 5 pairs of legs as a member of the order Decopoda, with one pair being its chelipeds (claws), where its left claw is larger than the right. Their carapace can be lightly green to completely white, and their eyes are black with small white spots.

Calcinus argus origins is in Hawaii. They are rarely found in the geographic division Indo-West Pacific; in shallow waters ranging from Eastern Africa to the Hawaiian Islands. Calcinus argus specimens were found and examined in the Mariana islands, along with 11 other Calcinus species by David Wooster.

Calcinus argus can be found in intertidal depths from the surface to around 40m, enough exposure to moving, clean salt water, and never in the deeper waters, preferring the reef; with the sea surface temperature in the 25-30 °C range, and sea surface salinity at 30-35 PSU. Calcinus argus can be found in reef or near the reef in branches of Acropora coral or Pocillopora coral.

Calcinus argus will protect its soft abdomen with a variety of shells, and when disturbed they will retreat into their shells, and fall into the middles of coral reef.

Source: Wikipedia: Calcinus argus — https://en.wikipedia.org/wiki/Calcinus_argus (CC BY-SA 4.0). Accessed 2026-09-25.