Heterostigmata
Taxonomic placing: Acari, Acariformes, Prostigmata.
Common name: None.
Morphology: A group of several superfamilies whose members are mostly small (about 0.2-0.3 mm), with several transverse dorsal shields. Only the females have prodorsal stigmata (hence “Heterostigmata”) near a pair of club-like sensory setae (often called pseudostigmatic organs). There are no eyes and the palpi are much reduced. Leg I is usually without claws, legs II-III with claws and an empodium, whereas leg IV may terminate in a strong claw or long setae. The sexes are very different from each other (sexual dimorphism).
Life cycle: These mites have a foreshortened life cycle. The free-living species have only two active stages, larvae and adults, whereas in the parasitic forms the females are the only active stage, giving birth to the daughter females. Reproduction is by arrhenotoky and the sex ratio is quite variable, being 95% females in some parasitic families. The feeding habits of the Heterostigmata are very diverse, some in the family Tarsonemidae being plant pests, others of this and other families subsist on fungi. Many Heterostigmata are associated with arthropods. These include parasites, like the Pyemotidae, which have been advocated for the biological control of pests, and pests of bees, like the tracheal mite, Acarapis woodi (Rennie).
References
Krantz, G.W. and Walter. D.E. (eds) 2009. A Manual of Acarology, 3rd Ed. Texas Tech University Press, Lubbock, Texas.
Lindquist, E. E. 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.
Lindquist, E.E. 1976. Transfer of Tarsocheyletidae to Heterostigmata, and reassignment of Tarsonemina and Heterostigmata to lower hierarchic status in the Prostigmata (Acari). Canadian Entomologist 108: 23-48.
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