Major mite taxa

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Taxonomy

updated 2025

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 Heterostigmata 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

Heterostigmata 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

Female Heterostigmata have prodorsal trichobothria (usually clubbed or globose in shape) are usually sclerotized and have a distinctive beige-color similar to astigmatid hypopi (see Astigmata heteromorphic stages fact sheet), but the latter have a ventral sucker plate and lack trichobothria.

Ecology and distribution

Most families of Heterostigmata 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 Heterostigmata. Within the Tarsonemoidea, the Podapolipidae are parasites of Coleoptera, Orthoptera and Hymenoptera. The Tarsonemidae have the most varied ecology of the Heterostigmata, 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

• Clift and Toffolon 1981Clift and Toffolon 1981:
  Clift AD, Toffolon RB. 1981. Biology, fungal host preferences and economic significance of two pygmephorid mites (Acarina: Pygmephoridae) in cultivated mushrooms, N.S.W., Australia. Mushroom Science 11: 245–253.
• Husband 1990Husband 1990:
  Husband RW. 1990. New species of Podapolipoides (Acari: Podapolipidae), ectoparasites of grasshoppers (Orthoptera: Acrididae) in Australia and New Zealand, with keys to world species. Annals of the Entomological Society of America 83: 371–393.
• Kethley 1982cKethley 1982c:
  Kethley JB. 1982c. Acariformes. pp. 142–145. In: Parker SP, ed. Synopsis and classification of living organisms, Vol. 2. McGraw-Hill, New York.
• Kethley 1990aKethley 1990a:
  Kethley JB. 1990a. Acarina: Prostigmata (Actinedida). pp. 667–756. In: Dindal DL, ed. Soil biology guide. John Wiley & Sons, Brisbane.
• Lindquist 1976Lindquist 1976:
  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). The Canadian Entomologist 108: 23–48.
• Lindquist 1986Lindquist 1986:
  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. Memoirs of the Entomological Society of Canada 136: 1–517.
• Mahunka 1967Mahunka 1967:
  Mahunka S. 1967. A survey of the scutacarid (Acari: Tarsonemini) fauna of Australia. Australian Journal of Zoology 15: 1299–1323.
• Moser 1975Moser 1975:
  Moser JC. 1975. Biosystematics of the straw itch mite with special reference to nomenclature and dermatology. Transactions of the Royal Entomological Society of London 127: 185–191.
• Moser and Cross 1975Moser and Cross 1975:
  Moser JC, Cross EA. 1975. Phoretomorph: A new phoretic phase unique to the Pyemotidae (Acarina: Tarsonemoidea). Annals of the Entomological Society of America 68: 820–822.
• Ochoa et al. 1991Ochoa et al. 1991:
  Ochoa R, Smiley RL, Saunders JL. 1991. The family Tarsonemidae in Costa Rica (Acari: Heterostigmata). International Journal of Acarology 17: 41–86.
• Ochoa et al. 1994Ochoa et al. 1994:
  Ochoa R, Aguilar H, Vargas C. 1994. Phytophagous mites of Central America: An illustrated guide. CATIE, Turrialba, Costa Rica.