The predation of the booklouse, Liposcelis entomophila (Enderlein) (Psocoptera; Liposcelidae) by the mite Blattisocius dentriticus (Berlese) (Acari; Ascidae) was studied in a series of laboratory experiments. Known numbers of mites and booklice were placed together in small tubes and counted after various durations. Fewer booklice were found in mite-infested tubes and it was possible to rear the mite on booklice, which supports the view that the mite is a natural predator of L. entomophila. Comparative susceptibility of the mite and booklouse to deltamethrin and fenitrothion was assessed by exposing both arthropod species to deposits of the two insecticides. The mite was found to be very susceptible to both deltamethrin and fenitrothion whereas the booklouse was only susceptible to the latter. The increased prevalence of L. entomophila in tobacco storage and grading buildings in recent years may therefore be attributed, at least in part, to the use of deltamethrin which suppresses its natural enemies.
