Major Mite Taxa
Mites are mostly minute (0.080 to 16 mm long as adults) chelicerate arthropods. Their closest relatives appear to be the Ricinulei and the Acari + Ricinulei comprise the Acarinomorpha, a subdivision of the Arachnida. Shared derived characters supporting this taxon include a hexapod larval stage and a distinct capitulum or gnathosoma (see Glossary for definition of unfamiliar terms).
Mites have been traditionally treated as a Subclass (Acari or Acarina) of the Class Arachnida composed of 2-3 orders. However, the recognition of the Acarinomorpha requires the demotion of the Acari or the invention of a new rank. Rather than coin new term for intermediate taxa, and since the analysis of relationships is still in flux, it seems best to leave the Acari rankless or to use the old 'subclass' for convenience.
The high diversity of the Acari and the large number of subdivisions necessary to accommodate all the taxa make for a complicated set of taxonomic ranks. At the present time, two superorders are recognized: the Acariformes and the Parasitiformes (including the once separate Opilioacarida).
Class Arachnida
Acarinomorpha
Ricinulei
(Subclass) Acari
Superorder Acariformes (Actinotrichida)
Superorder Parasitiformes (Anactinotrichida)
The Parasitiformes has about 15,000 described species in four distinct orders: Opilioacarida (=Tetrasigmata, Notostigmata), Ixodida (= Metastigmata, ticks), Holothyrida (=Holothyrina), and Mesostigmata (=Gamasida). Only the latter has more than one suborder. The Mesostigmata is divided into three suborders: Sejida, Trigynaspida, and Monogynaspida. Sejida contains a single supercohort, but Trigynaspida is divided into two supercohorts (Cercomegistina, Antennophorina) and Monogynaspida into five supercohorts (Microgyniina, Uropodina, Heterozerconina, and Gamasina). Cohorts and families especially important in quarantine are in red.
Superorder Parasitiformes
Order Opilioacarida - Opilioacaridae
Order Holothyrida - Allothyridae, Holothyridae, Neothyridae
Order Ixodida - Argasidae, Ixodidae, Nuttalliellidae
Order Mesostigmata
Suborder Sejida (Sejoidea)
Suborder Trigynaspida (Cercomegistina, Antennophorina)
Suborder Monogynaspida (Microgyniina, Heatherellina, Uropodina, Heterozerconina, Gamasina)
The Acariformes contains about 40,000 described species of mites arranged in two orders: Trombidiformes and Sarcoptiformes. The Trombidiformes includes the suborders Sphaerolichida and Prostigmata (=Actinedida). the Sarcoptiformes includes the suborders Endeostigmata and Oribatida (=Cryptostigmata, Oribatei). The latter includes the very important cohort Astigmatina (=Astigmata, Acaridida).
Superorder Acariformes
Order Trombidiformes
Suborder Sphaerolichida (Lordalychidae, Sphaerolichidae)
Suborder Prostigmata (Labidostommatides, Eupodides, Anystides, Eleutherengoinides)
Order Sarcoptiformes
Suborder Endeostigmata (Bimichaeliina, Nematalycina, Terpnacarina, Alicorhagiina)
Suborder Oribatida (Palaeosomatides, Enarthronotides, Parhyposomatides, Mixonomatides, and:
Supercohort Desmonomatides
Cohort Nothrina
Cohort Brachypylina
Cohort Astigmatina (= Astigmata, Acaridida))