Cheyletini

Dorsal view of Hemicheyletia wellsi, copyright Qing-Hai Fan.

Belongs within: Cheyletidae.
Contains: Cheyletus.

The Cheyletini is a group of predatory mites found free-living or in association with animal nests. The group is characterised by plesiomorphic characters for the family Cheyletidae and is potentially paraphyletic with regard to other subgroups of the family. The southern Asian genus Hylopecheyla is parasitic, found in association with squirrels and tree shrews, and possesses relatively short tarsi. The genera Tutacheyla, Laeliocheyletia, Cheletomimus and Hemicheyletia form a group of genera with relatively short legs, four setae on the palpal femur and very short guard setae on tarsi I, typically found living on trees (Bochkov & Fain 2001).

The tiny lurking fear
Published 3 August 2018

The world of micro-organisms can be a cut-throat one. Minute grazers are under constant threat from minute predators. It can be an existence red in tooth and claw or, in the case of today’s subjects, haemolymph-covered in chelicera and grasping seta.

The domestic cheyletid Cheyletus eruditus, from here.

The Cheyletini are one of fifteen tribes recognised by Bochkov & Fain (2001) in the mite family Cheyletidae. Cheyletids are small mites, generally less than half a millimetre in length, that are close relatives of the follicle mites seen on this site previously. Many cheyletids (including most Cheyletini) are, nonetheless, voracious predators of other mites. Other members of the family live as parasites on birds or mammals. In the past, such parasitic forms were recognised as a distinct family Cheyletiellidae but it is now recognised that they are descended from predatory ancestors, possibly on more than one occasion.

Predatory cheyletids are not to be sniffed at: the Hemicheyletia wellsina nymph on the left has managed to bring down another much larger predatory mite Metaseiulus occidentalis. Copyright Haleigh Ray.

The Cheyletini can be considered representative of this ancestral form; indeed, as members of the tribe are distinguished from others in the family solely by their retention of features likely to be primitive, it is likely to be non-monophyletic (Bochkov & Fain 2001). Cheyletini have more or less oval or oblong bodies with moderate-length legs, shorter than the length of the body, all tipped by a claw. The gnathosoma (the front section of the body bearing the chelicerae and palps) is well developed and generally makes up a full third of the body length. The palps are the real business end of a cheyletin, though. In many groups of prostigmatic mites, the last segment of the palp (the tarsus) is offset from the main line of the appendage and opposed to a large claw at the end of the tibia, the two of them together functioning to grab whatever the mite wishes to grab. Predatory cheyletids have the tibial claw and offset tarsus but the tarsus also bears a number of intimidating enlarged, claw-like setae that add to the mite’s grabbing power. In the Cheyletini, there are four such setae at the end of the tarsus, a pair of comb-like setae dorsally and a pair of sickle-shaped setae ventrally. The mite will generally sit in place, motionless, with its palps held open. Should a potential prey animal come close enough to the predator, the palps will swing together and the prey will be caught.

Cheyletini are diverse in habitat. Many genera are free-ranging hunters on trees but others show preferences for more constrained locales. In particular, a group of genera centred around the type genus Cheyletus includes species living in the nests and burrows of mammals and birds. Most of these species benefit their hosts by hunting down potential parasites and the like or cleaning up organic residue. One genus, Cheletophyes, is found in the nests of carpenter bees Xylocopa and can actually be transported between nests by the host bee in special pockets on the thorax called acarinaria. However, it is not that big a step to take from feeding on shed organic particles in the host’s nest to feeding more directly on the host itself and this is presumably how some cheyletids made the switch to parasitism. One member of the Cheyletini, Pavlovskicheyla platydemae, is an ectoparasite of tenebrionid beetles, attaching to them in spots concealed beneath the host elytra (Walter et al. 2009).

Female Hemicheyletia wellsina patrolling near her batch of eggs (in the upper left, under a protective silk covering she has woven for them), copyright Haleigh Ray.

Other Cheyletus species are known from human-associated habitats such as in houses or grain stores where, again, they are usually considered a net benefit due to their controlling effect on pests such as dust mites or flour mites. Indeed, the common species Cheyletus eruditus has been commercially marketed for control of stored product pests under the name Cheyletin. Females of this species in domestic habitats lay their eggs in crevices or other such concealed spaces and remain to guard their brood, driving away other animals that may pose a threat. However, hatching offspring need to disperse quickly, as if they hang around the nesting site too long they may be eaten by the mother herself (Walter & Krantz 2009).

Systematics of Cheyletini

Characters (from Bochkov & Fain 2001): Female with gnathosoma well developed, about 30%, or more, length of idiosoma, without protrusions. Gnathosomal apex with short median protuberances. Palpai tarsi with two dorsal comb-like setae and two ventral well-developed sickle-like setae. Palpai slender, claws slightly curved medially, with or without teeth. All setae of palpal tibia hair-like or lanceolate. Palpal femur and palpal genu not fused, without protrusions, bearing altogether five setae. Idiosoma ovoid or rhombus-like. Eyes present or absent. Shoulder-like projections of idiosoma absent. All idiosomal setae not exceeding half of idiosomal length. Neotrichial setae present or absent. Length of all legs not exceeding idiosomal length. Legs IV normally developed. Tarsi slender, with knobs not covering pretarsus or without knobs. Guard seta of tarsus I hair-like, variable in length, solenidion ω1 situated in basal half of tarsus I. Tibia I with solenidion. Tibia II with or without solenidion. Genu I with rod-like solenidion. Seta vI of tarsus I situated almost at same level as solenidion ω1 and guard seta. Pretarsus and claws present on all legs. Apical setae of tarsus I normally long. Tarsal setae p’ and p” II-IV hair-like. Coxae III with two setae. Trochanters I-IV with one seta. Distance between coxae II and III less than half of idiosomal width. Male with palpal tarsus with two comb-like and two sickle-like setae.

<==Cheyletini
    |  i. s.: Cheletophyes Oudemans 1904BF01
    |           |--*C. vitzthumi Oudemans 1914B49
    |           |--C. apicolaWB02
    |           |--C. hawaiiensis Baker 1949B49
    |           |--C. marshalli Baker 1949B49
    |           |--C. philippinensis Baker 1949B49
    |           `--C. semenovi Kuzin in Rodendorf 1940B49
    |         Lepidocheyla Volgin 1963BF01
    |         AnthribicheylaBF01
    |--Hylopecheyla Fain 1972BF01
    |--Paracheyletiella Kuznetsov 1977BF01
    |--Nodele Muma 1964BF01
    |    `--N. calamondin Muma 1964E-VVM-M07
    |--Paracheyletia Volgin 1955BF01
    |    |--P. assimilisE62
    |    |--P. pyriformisE62
    |    |--P. virginiensisE62
    |    `--P. wellsiE62
    |--+--Cheletacarus Volgin 1961BF01
    |  |    `--C. rugosus (Womersley 1941) [=Cheletophanes rugosa, Cheletonella rugosa]H98
    |  `--Cheletophanes Oudemans 1904BF01
    |       |--*C. montandoni (Berlese & Trouessart 1889) [=Cheyletus montandoni]B49
    |       `--C. peregrinus Berlese 1921B49
    |--+--Ker Muma 1964BF01
    |  |    |--K. palmatusE-KO07
    |  |    `--K. summersiA-T96
    |  `--Pavlovskicheyla Volgin 1965BF01
    |       |--P. platydemae Thewke & Enns 1975BF01
    |       `--P. semenoviBF01
    |--+--Zachvatkiniola Volgin 1969BF01
    |  |--Camincheyletus Smiley & Whitaker 1981BF01
    |  |--CheyletusBF01
    |  |--Cheletonella Womersley 1941BF01
    |  |    `--*C. vespertilionis Womersley 1941B49
    |  `--Eucheyletia Baker 1949BF01
    |       |--*E. bishoppi Baker 1949B49
    |       |--E. flabellifera (Michael 1878) (see below for synonymy)B49
    |       |--E. hardyi Baker 1949B49
    |       |--E. harpyia (Rodendorf 1940) [=Cheyletia harpyia]B49
    |       `--E. womersleyi Volgin 1963H98
    `--+--Tutacheyla Corpuz-Raros 1972BF01
       |--Laeliocheyletia Summers & Price 1970BF01
       |--Cheletomimus Oudemans 1904BF01
       |    |--C. berlesei Oudemans 1904H98 [=Cheletes berleseiB49; incl. *Cheletomimus trux Oudemans 1904B49]
       |    `--C. wellsigiDPD16
       `--Hemicheyletia Volgin 1969BF01
            |--H. anarboraTE79
            |--H. bakeri (Ehara 1962) [=Paracheyletia bakeri]H98
            |--H. bregatovaeTE79
            |--H. congensisTE79
            |--H. cordovensisTE79
            |--H. darwinia Summers & Price 1970TE79
            |--H. granulaTE79
            |--H. kysenyiensis Thewke & Enns 1979TE79
            |--H. lindquisti Thewke & Enns 1979TE79
            |--H. mexicana Thewke & Enns 1979TE79
            |--H. reticulataTE79
            |--H. rostellaTE79
            |--H. scitula Corpuz-Raros 1972C-RSV-S88
            |--H. scutellataTE79
            |--H. serrulaTE79
            |--H. volginiTE79
            |--H. wellsi (Baker 1949)TE79 [=Cheyletia wellsiH98]
            `--H. wellsinaTE79

Eucheyletia flabellifera (Michael 1878) [=Cheyletus flabellifer, Cheletia flabellifera, Cheyletus (Cheyletia) flabellifer]B49

*Type species of generic name indicated

References

[A-T96] Abo-Taka, S. M. 1996. Mites inhabiting poultry farms in Egypt. In: Mitchell, R., D. J. Horn, G. R. Needham & W. C. Welbourn (eds) Acarology IX vol. 1. Proceedings pp. 97–99. Ohio Biological Survey: Columbus (Ohio).

[B49] Baker, E. W. 1949. A review of the mites of the family Cheyletidae in the United States National Museum. Proceedings of the United States National Museum 99 (3238): 267–320.

[BF01] Bochkov, A. V., & A. Fain. 2001. Phylogeny and system of the Cheyletidae (Acari: Prostigmata) with special reference to their host-parasite associations. Bulletin de l’Institut Royal des Sciences Naturelles de Belgique Entomologie 71: 5–36.

[C-RSV-S88] Corpuz-Raros, L. A., G. C. Sabio & M. Velasco-Soriano. 1988. Mites associated with stored products, poultry houses and house dust in the Philippines. Philippine Entomologist 7 (3): 311–321.

[DPD16] Dabert, M., H. Proctor & J. Dabert. 2016. Higher-level molecular phylogeny of the water mites (Acariformes: Prostigmata: Parasitengonina: Hydrachnidiae). Molecular Phylogenetics and Evolution 101: 75–90.

[E62] Ehara, S. 1962. Mites of greenhouse plants in Hokkaido, with a new species of Cheyletidae. Annotationes Zoologicae Japonenses 35 (2): 106–111.

[E-KO07] El-Kammah, K. M., & L. M. I. Oyoun. 2007. Taxonomic records of mite species associated with animal and poultry farms in the Nile delta, vally and N. Sinai Egypt. In: Morales-Malacara, J. B., V. M. Behan-Pelletier, E. Ueckermann, T. M. Pérez, E. G. Estrada-Venegas & M. Badii (eds) Acarology XI: Proceedings of the International Congress pp. 223–232. Instituto de Biología and Faculdad de Ciencias, Universidad Nacional Autónoma de México, Sociedad Latinoamericana de Acarología: México.

[E-VVM-M07] Estrada-Venegas, E. G., I. M. Vázquez & J. A. Moreno-Moreno. 2007. Prostigmatid mites (Acarida: Prostigmata) in decaying wood from “La Mancha” Veracruz, Mexico. In: Morales-Malacara, J. B., V. M. Behan-Pelletier, E. Ueckermann, T. M. Pérez, E. G. Estrada-Venegas & M. Badii (eds) Acarology XI: Proceedings of the International Congress pp. 691–695. Instituto de Biología and Faculdad de Ciencias, Universidad Nacional Autónoma de México, Sociedad Latinoamericana de Acarología: México.

[H98] Halliday, R. B. 1998. Mites of Australia: A checklist and bibliography. CSIRO Publishing: Collingwood.

[TE79] Thewke, S. E., & W. R. Enns. 1979. Three new species of Hemicheyletia Volgin (Acarina: Cheyletidae) with a key to known world species. Journal of the Kansas Entomological Society 52 (1): 218–225.

[WB02] Walter, D. E., J. J. Beard, K. L. Walker & K. Sparks. 2002. Of mites and bees: a review of mite-bee associations in Australia and a revision of Raymentia Womersley (Acari: Mesostigmata: Laelapidae), with the description of two new species of mites from Lasioglossum (Parasphecodes) spp. (Hymenoptera: Halictidae). Australian Journal of Entomology 41: 128–148.

Walter, D. E., & G. W. Krantz. 2009. Oviposition and life stages. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 57–63. Texas Tech University Press.

Walter, D. E., E. E. Lindquist, I. M. Smith, D. R. Cook & G. W. Krantz. 2009. Order Trombidiformes. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 233–420. Texas Tech University Press.

Leave a comment

Your email address will not be published. Required fields are marked *