Major mite taxa

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Taxonomy

updated 2025

Common names

hypopus (hypopi), hypopode

Probability of encounter

high

Quarantine importance

Many Astigmatina of quarantine importance have a specialized dispersal stage, the heteromorphic deutonymph, that lacks functional mouthparts, has a closed gut and reduced capitulum, and usually a sucker plate (or pair of claspers) for attaching to an arthropod (or vertebrate); a few are able to enter the pores in vertebrate skin.

Diagnosis

Beige, pinkish to dark brown; hemispherical to flattened, usually oval in outline, well sclerotized, with distinct sejugal suture. Prodorsal trichobothria and pteromorphs absent. Capitulum tubular to button-like, without functional mouthparts; palps reduced to setiform appendages. Venter usually with well developed sucker plate.

Similar taxa

Heterostigmata (Prostigmata) often attach to arthropods and could be confused with astigmatan hypopi, especially Scutacaridae, but the latter lack the sucker plate and have a well-developed gnathosomal capsule.

Ecology and distribution

Hypopi (singular hypopus) are deutonymphs that act as special dispersal morphs of some astigmatans. Because they do not look like other stages, they are called heteromorphic deutonymphs. Another term used for this stage by some authors is hypopode.

Hypopi usually do not feed and hence have no mouthparts or anal opening. The capitulum is reduced to a small tubular or button-like structure, often with a few seta-like processes (true setae and the remnants of the palps). In a few cases, e.g., some endodermal parasites of vertebrates, the hypopi absorb nutrients through their skin. Most hypopi disperse by attaching to an insect or other arthropod (rarely lizards) using a complex sucker plate near the rear of the venter. This sucker plate is highly distinctive—if you see it you know that you have some kind of hypopal astigmatan. Formation of the hypopal stage is usually facultative in response to deteriorating environmental conditions. Most vertebrate parasites and some common stored product astigmatans have completely lost the ability to form hypopi (e.g., species of Tyrophagus).

References

• Houck and OConnor 1991Houck and OConnor 1991:
  Houck MA, OConnor BM. 1991. Ecological and evolutionary significance of phoresy in the Astigmata. Annual Review of Entomology 36: 611–636.
• Hughes 1976Hughes 1976:
  Hughes AM. 1976. The Mites of Stored Food and Houses (2nd ed.). Ministry of Agriculture, Fisheries and Food, Technical Bulletin 9. Her Majesty's Stationery Office, London.
• Krantz 1978Krantz 1978:
  Krantz GW. 1978. A manual of acarology [2nd ed.]. Oregon State University Book Stores, Corvallis.