Is it a mite?

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Nomenclature

Ricinuleida (Ricinulei)

Common names

ricinuleids

Probability of encounter

low

Quarantine importance

No known importance, although of potential conservation concern as threatened cave or rainforest dwelling species.

Similarity to mites

Hexapodhexapod:
with three pairs of legs (i.e. 6 legs), as in the larvae of mites or the larviform stages of others.
larvae, gnathosomagnathosoma:
(= capitulum) the anteriormost part of a mite or ricinuleid, composed of the cheliceral and pedipalpal segments and separated from the body (idiosoma) by a ring of soft cuticle.
, more or less mite-like build; however, ricinuleids have opisthosomas with three series of dorsaldorsal:
relating to the upper or back side; opposed to ventral.
sclerites and clear ventralventral:
relating to the lower or under side; opposed to dorsal.
segmentation.

Morphology

Normal adult length: <10 mm
Bodybody:
the idiosoma of mites.
tagmata: gnathosomagnathosoma:
(= capitulum) the anteriormost part of a mite or ricinuleid, composed of the cheliceral and pedipalpal segments and separated from the body (idiosoma) by a ring of soft cuticle.
, prosomaprosoma:
(= cephalothorax) the anterior body region in arachnids; usually not distinct in mites.
, idiosoma
Eyes: lens absent (pigment spot may be present)
Antennae: absent
Mouthparts: 2-segmented chelicerae; long, elbowedelbowed:
bent as in the arm at the elbow; geniculate.
palps
Legs: 4 pairs (3 pairs in larvae); tarsitarsus:
(pl. tarsi) the subdistal leg segment between the tibia and the pretarsus (apotele).
I & II with sensory pits
Distinguishing features: cucullus (shelf over mouthparts), elbowedelbowed:
bent as in the arm at the elbow; geniculate.
palps, postabdomen

Comments: Ricinuleids and mites (Acari
Factsheet for:Acari
Glossary:Opilioacariformes:
an obsolescent supraordinal term used for the Opilioacarida.
) are the only arthropods with a capitulumgnathosoma:
(= capitulum) the anteriormost part of a mite or ricinuleid, composed of the cheliceral and pedipalpal segments and separated from the body (idiosoma) by a ring of soft cuticle.
, i.e., with the cheliceralcheliceral:
of or pertaining to the chelicera.
and pedipalpal segments separated from the remainder of the prosomaprosoma:
(= cephalothorax) the anterior body region in arachnids; usually not distinct in mites.
by a circumcapitular groove.

Diversity

1 family (Ricinoididae), 3 geographically +/- discrete genera (Brazil to Honduras: Cryptocellus; Panama to Texas: Pseudocellus; Africa: Ricinoides), >55 spp.

References

• Harvey 2003