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).