These mites usually kill young bee larvae and feed on provisioned pollen and nectar. In nests with partitions (Osmia), bees that develop in the innermost cells chew their way out of the nest, and phoretic deutonymphs from the opened cells may attach to them. The mites in the innermost cell may die because of their inability to break through the partition. In nests without partitions (Lithurgus), some young bees may complete development and transform to adults that disperse the mites.
In colonies of Osmia cornifrons managed for pollination of blueberries in the USA, Ch. krombeini phoretic deutonymphs could disperse from a nest to nearby nests by walking through nest entrances and holes made by parasitic wasps. Cross-nest dispersal via blueberry flowers visited by multiple individuals of O. cornifrons was proven to be negligible (Park et al., 2009).
The presence of the inert non-phoretic deutonymph along with the phoretic deutonymph is the most conspicuous feature in the life-cycle of this genus. The inert deutonymph is a highly regressive, cyst-like morph with legs and most setae greatly reduced (Fig. 4). It is capable of surviving in old bee nests and infesting new hosts that reuse these nests or the nest material. When mites are trapped in the innermost cells of an infested nest or all bee larvae are killed and therefore cannot transfer mites to a new nest as adults, inert deutonymphs can be very important for mite survival.
Biology has been studied for Chaetodactylus osmiae (Chmielewski, 1993; Fain, 1966; Lith, 1957; Popovici-Baznosanu, 1913), Ch. birulai (Lith, 1957), and Ch. krombeini (Krombein, 1962, 1967).