Species of Forcellinia are primarily associated with ants (Formicidae), living in their nests as feeding stages and dispersing on adult ants as phoretic deutonymphs. For example, F. wasmanni feeds on dead ants and organic detritus in the lower level of ants' nests. Some species develop large population sizes in nests of honey bees (Apis) and stingless bees (Meliponini). They may occasionally occur in house dust (Forcellinia galleriella) (Andrews et al., 1995) and stored products such as dried milk (Forcellinia breviseta), in forest litter or under bark (Forcellinia diamesa), and in sweepings from grain stores and rotting potatoes. Feeding habits are unknown, but they presumably feed on decomposing organic matter and fungi. It is unlikely, although not entirely impossible, that Forcellinia species may attack pollen. Most bees store pollen in sealed cells, and it appears that Forcellinia lacks adaptations to either penetrate the sealed cells or sneak into them before they are sealed.
Two described and one undescribed species are known from nests of honey bees: Forcellinia galleriella (Apis mellifera), Forcellinia faini (Apis mellifera and Apis cerana), Forcellinia sp. (beehives in Hong Kong) (Bowman and Ferguson, 1985; Delfinado-Baker and Baker, 1989). Forcellinia galleriella probably opportunistically invaded beehives from an ant nest. The second species (F. faini) is probably more specific to bees (there are several repetitive records from different countries), although its potential associations with ants cannot be ruled out. In Thailand, these mites were very common in beehive debris of Apis cerana but were never found in close associations with the bees (Fain and Gerson, 1990).
In Costa Rica and Brazil, we observed that Forcellinia was common in two nests of stingless bees, probably feeding on fungi growing in abundance in old nest material. In both cases, an active ant nest was present inside or immediately nearby the bee nest, suggesting that occurrence of Forcellinia in nests of meliponine stingless bees is attributable to mites' spill-over from ant nests rather than to their long-term associations with bees. We hypothesize that since phoretic deutonymphs of Forcellinia have never been found on adult bees to date, it is likely that dispersal of these mites to beehives can be accomplished by ants entering bee nests in search for food but not by bees themselves.