The Oribatoidea (moss-mites) are characteristic of moss habitat. They are abundant on freshly burned-over land. The author notes the carrying of fungous spores by many groups of moss-mites and by related groups; the Udetaliodes and Galumninae lodge spores in their leg-cupboards, and certain species ingest spores. As these animals leave the earth at night and ascend vegetation, they may be efficient vectors of plant diseases. The origin of the groping habit in these eyeless mites is briefly discussed. Other Acarina, with eyes, have the habit of the characteristic movement of the anterior leg, used by these as a sensory act. Two instances of mutation, both in "ornate" and presumably decadent genera, are reported.