In tests of acaricides for the control of a Tyroglyphid mite, Aleuroglyphus ovatus (Troupeau), infesting cultures of the oriental rat flea, Xenopsylla cheopis (Roths.), in jars provided with linen covers and containing Purina dog food in sand as the rearing medium, Tedion and Kelthane proved ineffective, but light infestations (100 cc. of medium inoculated with 500 mites) were satisfactorily controlled by chlorobenzilate at 0·2 p.p.m. in the rearing medium or as a 0·05 per cent, solution in acetone painted on to the inner wall of the jar and used to soak the linen cover for three seconds. Heavy infestations (100 cc. medium inoculated with 2,000–3,000 mites) were controlled by chlorobenzilate at 20 p.p.m. in the medium or as a 0·5 per cent, solution applied to both the linen cover and the inner rim of the jar; a combination of both treatments (using 2 p.p.m. and a 0·5 per cent, solution) gave adequate control for 30 days.

The flea larvae were unaffected by 2 p.p.m. chlorobenzilate in the rearing medium; 20 p.p.m. killed larvae, but not adults. Neither stage was affected by treating the linen cover and inner rim of the breeding jar with a 0·5 per cent, solution of chlorobenzilate.

Measures are recommended for maintaining flea cultures free from mites, based on these experimental results and on a year's practice.