Pyemotes

 

HARMFUL | NOT HARMFUL | UNCERTAIN

generalist parasite; feeds on host hemolymph

Name and classification

Pyemotes Amerling, 1862

Taxonomy
Superorder Acariformes » Order Trombidiformes » Suborder Prostigmata » Infraorder Eleutherengona » Hyporder Heterostigmata » Family Pyemotidae » Genus Pyemotes

Type species
Pyemotes Eccoptogasteri pruni Amerling, 1861 nom. nud. (=? Pyemotes scolyti Oudemans, 1936)

Common synonyms
Pediculoides in historical literature

Common names
Sometimes called itch mites for their ability to bite humans; for example, the oak leaf gall mite or itch mite (Pyemotes herfsi) and straw itch mite (Pyemotes tritici).

Diagnosis

Adult: Tarsus I with single claw (Figs. 2, 6). Trochanters of legs I-IV each with 1 seta (Figs. 2, 6). Trochanter IV subtriangular (Figs. 2, 6). Coxisternal (=coxal) plates I-II together with maximally 4 pairs of setae (Fig. 2).

Female: Femur and genu of legs IV separate (Figs. 2, 6). Tarsus IV with paired claws and empodium (Fig. 2). Coxisternal plates I lacking discoid structures (Fig. 2). Coxisternal plates III-IV separated from each other medially by soft cuticle that bears a separate triangular sternal plate (Fig. 2).

Male: Legs IV 5-segmented (trochanter, femur, genu, tibia, and tarsus), with single claw; differentiated from legs III in being somewhat stouter and ending with a single sessile claw (Fig. 6). Gnathosoma not reduced, with palps (Fig. 6).

Distribution

Cosmopolitan, but species attacking bees have not yet been found in the Afrotropics.

Bee hosts

Apis, Anthophora (Apidae), Frieseomelitta, Melipona, Tetragonisca (Apidae: Meliponini), Hoplitis, and Megachile (Megachilidae)

Host association level

Permanent

associated exclusively with bees or their close relative, wasps; cannot live without these hosts

Temporary

some life stages are associated with bees, while others are not

Facultative or opportunistic

can complete entire life cycle without bees or their close relative, wasps

facultative

Host associations, feeding, and dispersal

  • All stages live in nests of bees and other habitats; there is no specificity toward bees.
  • Fertilized females parasitize larvae, pupae, or adult insects by injecting neurotoxin-containing saliva, which causes paralysis and eventual death, and enables the gravid female mites to feed on the host's hemolymph.
  • Mated females disperse to find new hosts. Dispersal occurs either on hosts (the scolyti-group is phoretic on bark beetles), mites' active movements, or by wind.

Biology

The genus Pyemotes includes polyxenous (multi-host) or monoxenous (single-host) insect parasites. 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 (Curculionidae: Scolytinae) and are not associated with bees.

Species of the ventricosus group are not known to be phoretic. At least some species possess venom. The mites inject neurotoxin-containing saliva into prey, which causes paralysis and eventual death, and enables the gravid female mites to feed on the host's hemolymph (Krczal, 1957). During feeding the female's posterior idiosoma becomes enlarged and ball-shaped (physogastry) (Figs. 3, 7), with the progeny developing inside. The host range includes a variety of hosts, and some species even attack and feed on pupae and adult insects. These mites often are dispersed by wind, and when they land on vertebrate hosts, they attempt to feed, resulting in bites. Bites of Pyemotes tritici can cause severe dermatitis on people handling infested material, such as hay. Contact with this mite can also produce asthma or nausea. Similarly, Pyemotes herfsi can bite humans, causing red, itchy, and painful wheals.

Records of Pyemotes from bees include Pyemotes ventricosus 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 (as ventricosus) from laboratory cultures of megachilid bees (Krombein, 1967); and Pyemotes herfsi from hives of Apis cerana in India (Dinabandhoo and Dogra, 1982). In the latter case, the mites were considered pests. In Brazil, Pyemotes tritici can destroy entire colonies of stingless bees (Tetragonisca angustula, Frieseomelitta varia, Melipona subnitida, and Melipona asilvai) and cause skin irritation in beekeepers (Menezes et al., 2009; Kerr et al., 1996; and Nogueira-Neto, 1997).