Genus Pyemotes Amerling, 1861, family Pyemotidae

Pyemotes tritici (Lagrèze-Fossat and Montané, 1851). Photograph by Eric Erbe; digital colorization by Chris Pooley. Identification by Ronald Ochoa

Fig. 1. Pyemotes tritici (Lagrèze-Fossat and Montané, 1851). Photograph by Eric Erbe; digital colorization by Chris Pooley. Identification by Ronald Ochoa. Click to enlarge

Bee Mites : Acari : Acariformes : Trombidiformes : Pyemotidae

Genus Pyemotes Amerling, 1861

Pyemotes Amerling, 1862: 54 (Type species Pyemotes Eccoptogasteri pruni Amerling, 1861 nom. nud. =? Pyemotes scolyti Oudemans, 1936 by monotypy); Krczal, 1957 (his synonymy)

Heteropus Newport, 1850: 71 (nom. preocc. by Fitzinger 1826 in Reptilia)

Type speices Pyemotes Eccoptogasteri pruni Amerling, 1861 nom. nud. =? Pyemotes scolyti Oudemans, 1936 by monotypy

Material (show database records).

General Description. The genus Pyemotes includes polixenous or monoxenous insect parasites exhibiting a wide variety of morphological polymorphisms. Some species of Pyemotes are natural enemies of forest insects or stored product insects. The genus is divided into two groups, scolyti and ventricosus (Cross et al., 1981).
Species of the scolyti group are phoretic on bark beetles (Scolytidae). At least one female morph is a phoretomorph. Phoretomorphic females are shorter than "normal" females and much broader, with thickened legs and enlarged claws. There are also two morphs in the male of Pyetomotes dimorphus Cross et Moser, 1975: "normal" and heteromorphic. The latter morph is distinctly larger, with many greatly enlarged setae, and sometimes setae are duplicated. The mites feed only on bark beetle brood or on immatures of other beetles in the subcortical habitats; none feeds on adults. They are relatively "venomless" and the host remaining alive for about a day after the initial attack (Cross and Moser, 1975).
Species of the ventricosus group are not known to be phoretic, and thus females are monomorphic. At least some species possess venom. The mites inject venom into prey, which causes paralisis and eventual death (Krczal, 1957). The host range includes a variety of hosts, and some species even attack and feed on pupae and adult insects. The bites of Pyemotes tritici (Lagrèze-Fossot et Montané, 1851) can cause severe dermatitis on people handling infested material such as hay. Contact with this mite can also produce asthma or nausea.
Records of Pyemotes from bees include Pyemotes ventricosus (Newport, 1850) from Anthophora retusa (Apidae) in England (Newport, 1850), Pyemotes anobii Krczal, 1957 from a colony of the European honey bee, Apis mellifera (Apidae) in the United States (Cross and Moser, 1975), Pyemotes beckeri Krczal, 1957 (as ventricosus) from laboratory cultures of megachilid bees (Krombein, 1967), and Pyemotes herfsi (Oudemans, 1936) from hives of Apis cerana in India (Dinabandhoo and Dogra, 1982). In the latter case, the mites were considered as pests. In Brazil, Pyemotes tritici (LaGrèze-Fossat & Montagné, 1851) can destroy entire colonies of stingless bees (Tetragonisca angustula, Frieseomelitta varia , Melipona subnitida, Melipona asilvai ) and cause skin irritation in beekeepers (Menezes at al., 2009; Kerr at al., 1996; Nogueira-Neto, 1997).
Pyemotes ventricosus, the type species of the genus, is poorly described and probably has been misidentified by subsequent workers. Oudemans (1937) speculated that the fungal disease of the bee larvae reported by Frison (1923) for Anthophora abrupta in the United States, is in fact physogastric females of Pyemotes ventricosus. Cross and Moser (1975) suggested that this species is only known from the original description and has never been recollected.

Hosts. Parasitizes insects of different orders

Notes. Some authors erroneously cite the year for this genus as "1862" and the type species as "Heteropus ventricosus Newport, 1850" (Khaustov & Perkovsky, 2010)

Distribution (show map). Cosmopolitan

Key to species of Pyemotes found on bee in North America
males*

Hysterosomal setae c₂ large, similar to d or e in size. Setae ip vestigial. Third prodorsal setae approximately twice as long as second prodorsal setae. On larvae of Anobiidae, Curculionidae, Buprestidae, Scolytidae, and Lyctidae (Coleoptera), vespid and sphecid wasps; laboratory colonies of megachilid bees. Holarctic

Pyemotes beckeri

Hysterosomal setae c₂ distinctly smaller than d or e. Length of third and second prodorsal setae variable.

2(1)

Setae c of femur IV short and slender, rarely reaching tip of tarsus IV, less than half as long as opisthosomal setae d and e. Third prodorsal setae not exceeding length of second prodorsal setae. Setae ip vestigial. On larvae of Anobiidae, Curculionidae, Buprestidae, Scolytidae (Coleoptera); colony of Apis mellifera. Holarctic

Pyemotes anobii

Setae c of femur IV long and stout, extending at least to, and usually beyond tarsus IV, more than half as long as opisthosomal setae d and e. Third prodorsal setae approximately twice as long as second prodorsal setae. Setae ip filiform, nearly as long as ax2. Nests of Hoplitis (Megachilidae) in Colorado

Pyemotes sp.

* Modified from Cross et al. (1981). In all species in the key the fourth prodorsal pair of setae being distinctly thinner than setae d and e.

Species associated with bees.

References

Amerling, C. 1861. Naturökonomie der von ihm beobachteten Milben, insbesondere der Trombidieen. Sitzungsberichte Der Königlich Böhmischen Gesellschaft Der Wissenschaften In Prague.2: 54-56.

Cross, E. A., J. C. Moser & G. Rack. 1981. Some new forms of Pyemotes (Acarina: Pyemotidae) from forest insects, with remarks on polymorphism. International Journal of Acarology.7: 179-196.

Cross, E. A. & J. S. Moser. 1975. A new, dimorphic species of Pyemotes and a key to previously-described forms (Acarina: Tarsonemoidea). Annals of the Entomological Society of America.68: 723-732.

Khaustov, A. A. & E. E. Perkovsky. 2010. The first fossil record of mites of the family Pyemotidae (Acari: Heterostigmata), with description of a new species of the genus Pyemotes from Rovno amber. Paleontological Journal.44: 418-421.

Krczal, H. 1957. Sytstematik und Ökologie der Pyemotiden. In Sytstematik und Ökologie Mitteleuropäischer Acarina. 1(1). ed. H.-J. Stammer, 385-823. Leipzig: Akademissche Verlaggesellschaft.

Krombein, K. V. 1967. Trap-nesting wasps and bees: life histories, nests, and associates. Washington, D.C: Smithsonian press. 570 pp.

Menezes, C., A. Coletto-Silva, G. S. Gazeta & W. E. Kerr. 2009. Infestation by Pyemotes tritici (Acari, Pyemotidae) caused death of stingless bee colonies (Hymenoptera: Meliponina). Genetics and Molecular Research.8: 630-634.

Newport, G. 1850. Further observations on the habits of Monodontomerus; with some account of a new Acarus, Heteropus ventricosus, a parasite in the nests of Anthophora retusa. Proceedings of the Linnean Society of London.2: 70-71.

Oudemans, A. C. 1936. Neues über Pediculoides Targ. Tozz. 1878 In Festschrift zum 60. geburtstage von professor dr. Embrik Strand. Ordinarius für Zoologie und Direktor des Systematisch-Zoologischen Instituts und der Hydrobiologischen Station der Universität Lettlands, Riga; Dr. rer. nat. h. c., M.A.N., F.R.E.S., F.L.S., F.Z.S., etc. Vol. 1, ed. E. Strand, 391-404. Riga: Izdevniecība "Latvija".

Image Gallery

Pyemotes tritici

Physogastric females of the mite Pyemotes sp. (Pyemotidae) parasitizing pupa of the bee Hoplitis albifrons argentifrons (Hymenoptera: Megachilidae) from Colorado

mites on bee

Pyemotes sp