Endeostigmata

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Taxonomy

Alycidae Canestrini & Fanzago 1877 (=Pachygnathidae Kramer 1877, Bimichaeliidae Womersley 1944Womersley 1944:
Womersley H. 1944. Australian Acarina, families Alycidae and Nanorchestidae. Transactions of the Royal Society of South Australia 68: 133–143.)

Diagnosis

Prodorsumprodorsum:
the dorsal surface of the propodosoma.
with 2 pairs of filiform trichobothriatrichobothrium:
(pl. trichobothria) (= bothridial sensillum) an often elaborately modified seta set in a cup-like base; forms include filiform, ciliate, pectinate or variously thickened or clubbed (bat-like to globose or capitate).
(si, ve) and 4 pairs of setaeseta:
(pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
(vi, se, in, exp); naso reduced to small nub, median eye absent; lateral eyes present. Rutellarutellum:
(pl. rutella) In Sarcoptiformes, the hypertrophied setae on the hypostome, often toothed; not to be confused with a corniculus (although possibly a homologue).  In Astigmata, the rutellum may be referred to as a pseudorutellum, although it is the same structure.  Various forms of rutella are recognized, including the atelebasic and pantelebasic.
present; chelicerae chelate-dentatechelate-dentate:
pincer-like chelicerae with teeth.
, each with 2 setaeseta:
(pl. setae, from L. = bristle) cuticular process composed of a hollow shaft (sometimes filled with a refractive material) produced from a membranous socket (the alveolus); the hair-like, spine-like, branched or variously expanded structures on the surfaces of the legs and body.  Most setae function as mechanoreceptors, but others (e.g., solenidia) are chemoreceptors or have unknown or ambiguous functions.
. Opisthosomaopisthosoma:
(= abdomen) the posterior body division in arachnids; usually not distinct in mites because of the fusion of the opisthosoma with part of the prosoma to form the idiosoma.
usually hypertrichous, but sometimes only sparsely so; 3 pairs of genital papillaegenital papillae:
 1-3 pairs of extrusible finger-like to button-like projections, usually retracted into in the genital vestibule of acariform mites; sometimes formed as sessile disks around the genital opening; thought to be osmoregulatory structures; modified or multiplied and dispersed over the body in many freshwater mites.  Genital papillae are absent in the larva, but may be added ontogenetically: protonymphs have one pair, deutonymphs two pairs, and tritonymphs (and adults) three pairs.  The tritonymphal pair of papillae is often lost.  The serially homologous Claparède's organ is usually present in the larvae (and prelarvae) of mites exhibiting genital papillae in nymphs and adults (Oudeman's Rule).
.

Remarks

Species of Alycus are fairly common and only likely to be confused with species of Amphialycus, which have retained a median eye. Some species of Alycus feed on nematodes (Walter 1988cWalter 1988c:
Walter DE. 1988c. Predation and mycophagy by endeostigmatid mites (Acariformes: Prostigmata). Experimental and Applied Acarology 4: 159–166.), which usually do not form visible gut contents, but others have gut boluses with fungal material.

References

• Grandjean 1936bGrandjean 1936b:
  Grandjean F. 1936b. Le genre Pachygnathus Dugês (Alycus Koch) (Acariens), ire partie. Bulletin du Muséum national d'histoire naturelle 8 (ser. 2): 398–405.
• Grandjean 1937aGrandjean 1937a:
  Grandjean F. 1937a. Le genre Pachygnathus Dugês (Alycus Koch) (Acariens). Deuxième partie. Bulletin du Muséum national d'histoire naturelle 9 (ser. 2): 56–61, figs 1–3.
• Grandjean 1937bGrandjean 1937b:
  Grandjean F. 1937b. Le genre Pachygnathus Dugês (Alycus Koch) (Acariens). Troisième partie. Bulletin du Muséum national d'histoire naturelle 9 (ser. 2): 134–138, figs 4–5.
• Grandjean 1937cGrandjean 1937c:
  Grandjean F. 1937c. Le genre Pachygnathus Dugês (Alycus Koch) (Acariens). Quatrième partie. Bulletin du Muséum national d'histoire naturelle 9 (ser. 2): 199–205, figs 6–8.
• Grandjean 1937dGrandjean 1937d:
  Grandjean F. 1937d. Le genre Pachygnathus Dugês (Alycus Koch) (Acariens), cinquième et dernière partie. Bulletin du Muséum national d'histoire naturelle 9 (ser. 2): 262–269, fig 9.
• Halliday 1998Halliday 1998:
  Halliday B. 1998. Mites of Australia: A checklist and bibliography. Monographs on Invertebrate Taxonomy, Vol. 5. CSIRO Publishing, Collingwood.
• Hammen 1969aHammen 1969a:
  Hammen L, van der. 1969a. Notes on the morphology of Alycus roseus C.L. Koch. Zoologische Mededelingen 43: 177-202.
• Judson 2000Judson 2000:
  Judson M. 2000. Nomenclatorial problems assoicated with the names Alycidae Canestrini & Fazago, 1877 and Pachygnathidae Kramer, 1877 (Acari). Memorie della Società Entomologica Italiana 78 (2): 533-540.
• Kethley 1982dKethley 1982d:
  Kethley JB. 1982d. Endeostigmata. pp. 118-120. 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.
• Kethley 1990bKethley 1990b:
  Kethley JB. 1990b. The prelarva of Alycus roseus Koch (Bimichaeliidae: Acariformes: Acari). Canadian Journal of Zoology 68 (5): 1058-1061.
• Kethley 1991Kethley 1991:
  Kethley J. 1991. Probable tritonymphal sexual dimorphism in Alycus roseus (Bimichaeliidae: Acariformes: Acari). Journal of Entomological Science 26 (1): 130-135.
• Krivolutski et al. 1978Krivolutski et al. 1978:
  Krivolutski DA, Livshits IZ, and Mitrofanov VI. 1978. Pachygnathidae. pp. 91-96. In: Gilyarov MS, ed. Identification key of soil-inhabiting mites, Trombidiformes. Nauka, Moscow.
• Thor and Willman 1941Thor and Willman 1941:
  Thor S and Willman C. 1941. Acarina - 71a. Eupodidae, Penthalodidae, Penthaleidae, Rhagidiidae, Pachygnathidae, Cunaxidae. Das Teirreich 71: 1-186.
• Walter 1988cWalter 1988c:
  Walter DE. 1988c. Predation and mycophagy by endeostigmatid mites (Acariformes: Prostigmata). Experimental and Applied Acarology 4: 159-166.
• Walter and Proctor 1999Walter and Proctor 1999:
  Walter DE and Proctor HC. 1999. Mites: Ecology, evolution and behaviour. University of NSW Press, Sydney and CABI, Wallingford. 494 pp.
• Womersley 1944Womersley 1944:
  Womersley H. 1944. Australian Acarina, families Alycidae and Nanorchestidae. Transactions of the Royal Society of South Australia 68: 133-143.
• Zakhvatkin 1949Zakhvatkin 1949:
  Zakhvatkin AA. 1949. New representatives of apparently segmented mites (Acarina: Pachygnathidae). Entomologicheskoe Obozrenie 30: 291-297.