The habitat and distribution of Arctoseius cetratus are summarised and details of feeding habits and phoresy given. Rearing of individual mites fed on sciarid eggs and of mass cultures is described. Phoretic females were fertile. Oviposition began 24 hours after detachment and mites produced 2.5 eggs/ day thereafter. Fewer eggs were laid by mites feeding on nematodes. Females reared in isolation produced no eggs. The surface of freshly laid eggs was camouflaged by the application of particles of the substratum. Larvae emerged within 5-6 days and matured after approx. 1 week.