Trochometridium

 

HARMFUL | NOT HARMFUL | UNCERTAIN

parasite and vector; infests brood cells and infects them with fungus, killing developing bees

Name and classification

Trochometridium Cross, 1965

Taxonomy
Superorder Acariformes » Order Trombidiformes » Suborder Prostigmata » Infraorder Eleutherengona » Hyporder Heterostigmata » Family Trochometridiidae » Genus Trochometridium

Type species
Trochometridium tribulatum Cross, 1965

Diagnosis

Female: First hysterosomal tergite C tripartite, with 2 lateral and 1 median lobes (Fig. 4). Femur I and genu I each with 5 setae (Fig. 7).

Other diagnostic characters

Female: With a pair of stigmata and associated tracheae anterolaterally on prodorsum and with a pair of capitate bothridial setae sc1 (Fig. 3). Peritremes absent. Opisthosoma usually with a longitudinal series of 4 dorsal overlapping plates (tergites). Tarsus I with single claw (Fig. 7). Tarsi II-III with stalked, smooth empodium, flanked by paired claws (Fig. 2). Legs IV with separate femur and genu (Fig. 2), with total of 5-12 setae on tibia and tarsus. Trochanters of legs I-IV each with a seta (Fig. 2). Trochanter IV quadrangular, slightly longer than wide, different in form from subtriangular trochanter III (Fig. 2). Female pharynx large, muscular, not divided into muscular sections. Prodorsum not covered posteriorly by tergite C (Fig. 4). Prodorsum with 3 pairs of filiform setae (v1, v2, sc2) (Fig. 3). Prodorsum with anterior pair of vertical setae (v1) inserted posterior to stigmata (Fig 3). Coxisternal (=coxal) plates I-II together with 6 pairs of setae (1a, b, c, 2a, b, c).

Species identification

A dichotomous key is available in Hajiqanbar et al., 2009. It includes all described species, of which two have been found on bees.

Distribution

Trochometridium tribulatum: Canada, USA, Mexico, Egypt, Sudan, and South Africa (Cross and Bohart, 1979; Lindquist, 1985; our data).

Trochometridium iranicum: Iran.

Species associated with non-bee hosts are distributed in the Palaearctic, Oriental and Australian regions.

Bee hosts

Trochometridium iranicum (halictid bee Pseudapis nilotica) and Trochometridium tribulatum (Calliopsis, Pseudopanurgus (=Anthemurgus) (Andrenidae), Halictus, Nomia, Sphecodes (kleptoparasitic bee; phoretic host only) (Halictidae), Megachile (Megachilidae), Diadasia, Exomalopsis, Melissodes, and Oreopasites (kleptoparasitic bee; phoretic host only) (Apidae))

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

permanent (Trochometridium iranicum) or mostly permanent (with a preference toward bees but host range includes non-bee hosts (Trochometridium tribulatum)

Host associations, feeding, and dispersal

  • All stages live in ground nests of bees and wasps, where they feed on fungi. Fungal spores are deposited in specialized sporothecae (pockets) on adult female body.
  • Mite females disperse on adult bees and transfer fungal spores to new nests.
  • Fungus kills developing bees in the new nest. Mites feed on the fungus and complete their life cycle.
  • Dispersing females probably can attach to different non-bee insects occurring in proximity of the nest in soil.

Biology

The dispersal stage is the adult female. The female has a pair of internal sacs called sporothecae between legs III and IV (Fig. 8). The sporothecae contain fungal spores that are transferred by the mite to provisioned cells of ground nesting bees such as Calliopsis, Nomia, Halictus, Anthemurgus, and Melissoides. The bee egg or young larva dies in the infested cell as a result of development of the fungus and mites. Mite eggs are laid instead of being retained within the physogastric mother. The eggs hatch into inactive larvae, which molt to males and females. The new generation of mites develops upon the fungal mycelium. The female is the only stage that feeds (Cross and Bohart, 1979; Lindquist, 1985; Neff and Rozen, 1995).

The host range for T. tribulatum includes wasps and beetles. Perhaps beetles become infested by mites dispersing from bees or wasps nesting in the same soil (i.e., the beetles are phoretic hosts only).