Vidia

 

HARMFUL | NOT HARMFUL | UNCERTAIN

probably beneficial; provides sanitary services by feeding on fungi on leaves that bees use as cell lining material

Name and classification

Vidia Oudemans, 1905

Taxonomy
Superorder Acariformes » Order Sarcoptiformes » Suborder Oribatida » Infraorder Desmonomata » Hyporder Astigmata » Family Winterschmidtiidae » Genus Vidia

Type species
Vidia undulata Oudemans, 1905

Diagnosis

Adult: Condylophores fused into a V-shaped sclerite in base of ambulacral stalk (Fig 13). Genu III without a dorsal solenidion (Fig. 14). Ambulacral stalk not narrowing apically before joining ambulacral disc (Fig 13). Dorsal hysterosomal setae long, extending to base of next posterior seta (Fig 8). Body cuticle smooth (Fig. 8). Tarsus I less than 4 times longer than it is wide (Figs. 12). Basal width of subcapitulum at least 2/3 the distance from base of subcapitulum to apex of palp (Fig 10).

Other diagnostic characters

Phoretic deutonymph: Setae ba I-II and aa I absent (correlates with character in adult) (Fig. 5). Pretarsal ambulacrum and empodial claw present on legs I-II (Fig. 5). Tarsi I-III with elongated membranous ambulacra (Fig. 7). Empodial claws I-III small and simple (Fig. 7). Empodial claw IV absent (Fig. 7). Leg IV shorter than leg III (Fig. 7). Tibiotarsus IV with 3 long apical setae (Fig. 7) and 3 short (2 foliate, 1 simple) (Fig. 7). Tarsus I with solenidia (ω1 and ω3) closely associated, usually in the basal half of the tarsus (Fig. 5). Solenidion ω2 vestigial, alveolar (Fig. 5). Coxal apodemes III fused together (Fig. 4). Ocelli absent on propodosoma (Figs. 1, 5). Tarsi I-II with 6 setae (e, f, d, ra, la, wa; p' absent), of which 3 foliate (ra, la, f), e short (Figs. 5, 6). Tibiae I-II with 2 ventral seta (Fig. 6). Femur IV with 1 ventral seta (wF) (Fig. 7). Genu III with seta nG (Fig. 7). Subcapitular remnant absent (Fig. 3). Palps present or absent (Fig. 3).

Adult: Pretarsal ambulacrum not greatly expanded (Figs. 12, 13). Prodorsum with external vertical setae (ve) absent (alveoli situated on middle of lateral sides of prodorsal shield) (Fig 11). Internal vertical setae (vi) at anterior edge of propodosoma (Fig. 11). Empodial claws present (Fig 12). Femur IV with 1 ventral seta (Fig. 14). Tarsi long, at least three times as long as wide (Fig. 12-14). Male without obvious striation pattern on hysterosoma. Tibiae I-II with 2 ventral seta (Fig. 12, 13). Long setae of hysterosoma not borne on angular protuberances (Fig. 8).

Species identification

The two Palaearctic species, Vidia lineata and Vidia undulata, can be identified using descriptions and illustrations from Fain, 1972. Nearctic species (Vidia hirsuta, Vidia latimanus, Vidia rubi, and Vidia texana) can be identified using OConnor and Eickwort, 1988. Trichotarsus bomborum Leonardi, 1900 probably belongs in Vidia. No key to species exists and many undescribed species have been collected.

Distribution

Cosmopolitan except for Antarctica: Holarctic, Neotropical, Afrotropical, Oriental, and Australian regions.

Bee hosts

This genus is primarily associated with leafcutting and resin bees (Megachile), but a few records are available from Hylaeus, bumble bees (Bombus), and honey bees (Apis).

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

  • Feeding stages live in nests of leafcutting bees (Megachile), where they occur on leaves that Megachile bees use for nest cell walls, and presumably feed on fungi.
  • Phoretic deutonymphs (non-feeding stage) disperse on adult bees from one nest to another. Kleptoparasitic bees (Coelioxys) are also used as transport.

Biology

Observations on Vidia rubi (OConnor and Eickwort, 1988), associated with ground-nesting Megachile rubi, suggest that Vidia does not harm the bee directly or indirectly, but instead stays on the leaves that Megachile bees use for nest cell walls, where the mites presumably feed on fungi. The mites do not occur on the bees' provision masses nor on the young bee larvae. In contrast, large numbers of Vidia texana have been found on prepupae of Megachile texana, which was originally interpreted as evidence for parasitism (Eickwort et al., 1981). However, it was later noted that mites aggregate on bee prepupae as they prepare to form the phoretic stage and disperse on the adult bee (OConnor and Eickwort, 1988).

The following account on the biology of Vidia is based on observations of Vidia rubi and Vidia texana (OConnor and Eickwort, 1988). Deutonymphs disembark from adult female bees when cells are provisioned or during or following oviposition. They crawl onto the leaves that form the cell's walls and make their way between tightly pressed leaf pieces, where they molt to tritonymphs. Tritonymphs (presumably) feed there and molt into adults, which mate. Female mites oviposit in the same location and larvae, protonymphs, and adults feed between the leaves, predominantly between the inner and middle leaf layers where surfaces are moist and mold may form. In cells with bee eggs or feeding larvae, the mites do not occur on the host immatures or provisions, and one generation is probable. At some point before the fully fed bee larva begins spinning its cocoon, the mites move onto its surface, either as protonymphs or deutonymphs. They remain there as deutonymphs after the cocoon is spun, clustering on the prothoracic dorsum of the host. They remain in this position while the post-defecating bee larva spends the winter in diapause. When the bee pupates in the spring, the mite deutonymphs transfer to the pupal surface, and likewise onto the adult bee's integument during the next ecdysis. The deutonymphs cluster ventrally on the adult bees. Deutonymphs that develop in cells containing male bees either transfer to female bees when their phoretic hosts copulate (as suggested by the mites' ventral position) or are lost to the population. Those on female bees disembark when their phoretic hosts make cells, to begin the cycle anew.

The records from other types of bees may involve accidental phoresy on an unspecific host (e.g., the record of Vidia undulata collected on the colletid bee Hylaeus conformis was not confirmed after examining a large series of this bee), taxonomical uncertainty (e.g., Trichotarsus bomborum from Bombus hortorum), or misidentifications (Vidia spp. from Apis spp. in India).