In Japan, an undescribed species of Tortonia was found to be a kleptoparasite of Osmia cornifrons, an important pollinator of apple trees (Qu et al., 2002; Qu et al., 2003): after infesting cells and prior to feeding on the stored pollen-mass, Tortonia sp. killed hosts, but only if the hosts were at stages egg to early third instar larva. The success of killing the host appears to positively depend on mite population sizes. Bees that survived formed normal cocoons.
Feeding stages and phoretic deutonymphs hibernate in bee nests. Protonymphs of Tortonia sp. that encountered shortages of food molted to phoretic deutonymphs. The percentage of phoretic deutonymphs phoretic on bees is lower (6.6% in total) as compared to Chaetodactylus.
Tortonia sp., when co-inhabiting with Chaetodactylus nipponicus in the same cell, shows lower population sizes, indicating its lower competitive ability. However, in cells with living hosts, the ratio of individual numbers of Tortonia sp. was higher than that of Ch. nipponicus, because the former can survive by feeding on host feces.
In the USA, mortality of developing wasps Monobia quadridens in cells infested with feeding stages of Tortonia quadridens has been observed, but the ultimate cause of death remains unknown. Mites have appeared to act as scavengers feeding on organic debris in the nests (Krombein, 1962; Krombein, 1967). Similarly, all stages of Tortonia quadridens were found in a nest of Xylocopa virginica, on and in the pollen balls in empty (failed) cells. The ultimate cause of cell failure remains uncertain. These authors called Tortonia kleptoparasitic (Lombert et al., 1987).