Medeus

 

HARMFUL | NOT HARMFUL | UNCERTAIN

potentially harmful; may kill developing bees or may simply prefer living in cells with dead bees

Name and classification

Medeus Volgin, 1974

Taxonomy
Superorder Acariformes » Order Sarcoptiformes » Suborder Oribatida » Infraorder Desmonomata » Hyporder Astigmata » Family Acaridae » Genus Medeus

Type species
Medeus vesparius Volgin, 1974

Diagnosis

Phoretic deutonymph: Posterior dorsum with well-developed longitudinal apodeme (Figs. 1, 3). Posterior apodemes IV extend posteriorly beyond level of trochanters IV (Fig. 2). Tarsus IV with one long seta (d) (Figs. 1, 2, 7). Coxal setae 1a, 3a, 4a filiform (not conoidal) (Fig 2). Coxal seta 4b absent. Posterior apodeme of coxal field II divided (Fig. 2). Claws I-IV slightly hooked (Figs. 2, 5, 6, 8). Tarsi I-II without setae ba I-II (Fig. 5). Setae aa (aa’’) absent from tarsus I (Fig. 5). Tibiae I-II with 1 seta each (gT I-II present, hT I-II absent) (Figs. 2, 6). Tibiae IV without ventral seta (kT IV absent) (Figs. 2, 8).

Adult: Posterior edge of prodorsal sclerite incised (Fig. 13). Coxal seta 4b absent (correlates with character in deutonymph) (Fig. 10). Setae ve situated nearly at the same level as setae vi, not barbed (Fig. 13). External and internal scapular setae (se, si) situated nearly on the same transverse line (Fig. 13). Grandjean's organ rounded and fimbriate (Fig. 12). Supracoxal setae scx simple (Fig. 13). Tibiae I with solenidion σ' not more than 3 times longer than σ'' (Fig. 14). Tibiae I-II with1 ventral seta (gT I-II present, hT I-II absent) (Fig. 14) (correlates with deutonymph). Tibiae IV without ventral seta (kT IV absent) (correlates with deutonymph) (Figs. 15, 16). Tarsal seta ba I present (not correlated with deutonymph) (Fig. 14). Tarsal seta ba II absent (correlates with deutonymph) (Fig. 14). Setae aa (aa’’) absent from tarsus I (correlates with deutonymph) (Fig. 14).

Species identification

This genus includes two described and one undescribed species. Adults of the two described species (Medeus vesparius and M. ithacaensis) can be distinguished using their original descriptions (OConnor, 1997; Volgin, 1974). Deutonymphs are known for M. ithacaensis and the undescribed species.

Distribution

Nearctic, Palaearctic, and Afrotropical regions

Bee hosts

apid bees of the genera Anthophora and rarely, Diadasia

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

Host associations, feeding, and dispersal

  • All stages live in nests of Anthophora bees, where they feed on pollen and fungi. Circumstantial evidence suggests these mites may kill developing bees.
  • Phoretic deutonymphs disperse on bee hosts.

Biology

Biological observations are available for Medeus ithacaensis (OConnor, 1997): Mites have been found only in cells with moldy provisions or dead bees. It is unknown, however, if the mites cause bee mortality or they simply prefer living in cells without bees (and later find cells with emerging bees in order to disperse). Gut content of the mites contained a mixture of crushed pollen and fungal spores, indicating that these mites can be potentially kleptoparasitic.