Eleutherengonides, Heterostigmatina
Superorder Acariformes
Order Trombidiformes
Suborder Prostigmata
Supercohort Eleutherengonides
Cohort (Superfamily): Heterostigmatina (Tarsocheyloidea, Heterocheyloidea, Pyemotoidea, Pygmephoroidea, Tarsonemoidea)
Common names: tarsonemids, pygmephorids, scutacarids, pyemotids, straw itch mites, red pepper mites, tracheal mites, broad mite, cyclamen mite.
Probability of Encounter: Very high
Quarantine importance: High. The Heterostigmatina contains a couple of important crop pests (broad mite, cyclamen mite) and some pests of ferns, mushroom culture (red pepper mites), and bees (tracheal mites), as well as parasitoids of insects, including those that sometimes bite people (straw itch mites).
Diagnosis. Heterostigmatina are minute to
medium-sized; usually well armored, with several large dorsal
sclerites; white, yellow, or brown in
color. Capitulum
typically head-like; cheliceral bases fused into a
single unit (stylophore) that may or may not be fused with the subcapitulum;
fixed digit of the chelicera absent, movable digit blade-like or styletiform. Palps linear and reduced
to 3 or fewer segments; palps may appear to be absent. In females stigmata open anterolaterally on
the ‘shoulders’ of the prodorsum, and the single pair of prodorsal
trichobothria is capitate; stigmata and trichobothria absent in males (except
Tarsocheyloidea); eyes absent.
Dorsal setation reduced, usually slender setae, but sometimes expanded,
leaf-like. Legs I
often with tarsal claw modified as a hook; legs IV in females often reduced or
absent; coxal fields fused to varying degrees so that apodemes form cross-like
patterns ventrally. Genital papillae
absent. Males often with
genital sucker for sequestering
pharate female. Many species exhibit
polymorphism related to phoresy and some are
physogastric.
Similar taxa.
Ecology & Distribution. Most families of Heterostigmatina are associated with insects or stored products. Tarsocheylids have been collected from the tunnels of bark beetles, beneath the elytra of passalid beetles, as well as from rotting wood. Heterocheylids are also passalid associates. Neither of these taxa is known to feed on their hosts. The interactions of Pygmephoroidea with their hosts are primarily phoretic, and the mites feed on fungus upon reaching their destination. In contrast, many species in the Pyemotoidea are parasites, parasitoids, and predators of insects. They are often found in infested stored products, and their mistaken biting of humans can cause severe itching and allergic reactions (‘hay itch’, ‘straw itch’, and ‘grocer’s itch’). Female morphs specialised for hanging on to their hosts – phoretomorphs occur in several families of pygmephoroids and pyemotoids. These polymorphisms have caused much taxonomic confusion within the Heterostigmatina. Within the Tarsonemoidea, the Podapolipidae are parasites of Coleoptera, Orthoptera and Hymenoptera. The Tarsonemidae have the most varied ecology of the Heterostigmatina, sometimes acting as parasites or predators of insects (the most famous of these being the honeybee parasite Acarapis woodi), sometimes as fungivores, and sometimes as plant parasites.
References
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Biology, fungal host preferences and economic significance of two pygmephorid
mites (Acarina : Pygmephoridae) in cultivated mushrooms, N.S.W., Australia. Mushroom
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Husband RW. 1990. New species of Podapolipoides
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Kethley JB.
1982. Acariformes. In: Parker, S.P. (ed.) Synopsis and Classification of Living
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1990. Acarina: Prostigmata
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Lindquist EE. 1976. Transfer of the
Tarsocheylidae to the Heterostigmata, and reassignment of the Tarsonemina and
Heterostigmata to lower hierarchic status in the Prostigmata (Acari). Can.
Entomologist 108: 23-48.
Lindquist EE. 1986. The world genera
of Tarsonemidae (Acari : Heterostigmata) : A morphological, phylogenetic, and
systematic revision, with a reclassification of family-group taxa in the
Heterostigmata. Mem. Ent. Soc. Can. 136: 1-517.
Mahunka S. 1967. A survey of the scutacarid (Acari :
Tarsonemini) fauna of Australia. Aust. J. Zool. 15: 1299-1323.
Moser JC. 1975. Biosystematics of
the straw itch mite with special reference to nomenclature and dermatology. Trans.
Roy. Ent. Soc., Lond. 127: 185-191.
Moser JC & Cross EA. 1975. Phoretomorph: A new phoretic phase unique to the Pyemotidae (Acarina : Tarsonemoidea). Ann. Ent. Soc. Amer 68: 820-822.
Ochoa, R., H. Aguilar & C. Vargas 1994. Phytophagous Mites of Central America: An Illustrated Guide CATIE, Turrialba, Costa Rica.
Ochoa R, Smiley RL, Saunders JL. 1991. The family Tarsonemidae in Costa Rica (Acari: Heterostigmata). Int. J. Acarol. 17: 41-86