A Method for Comparing Fly-Repellant Sprays

Abstract

In a standard technique for comparing two fly-repellant sprays, batches of mice are treated with the two materials under test and are subsequently exposed under anaesthetic to attack by flies of the genus Stomoxys. A control untreated batch is similarly exposed for purposes of comparison. If replicate tests are carried out on several occasions, it is found that the attack rates in the control and in the treated mice vary considerably, and the problem arises of finding some stable basis for comparison. In practice, five mice are used on each occasion for each treatment and for the controls, and each mouse is exposed to attack by 20 flies (this figure is not exact, but the variations in the number of flies are small enough to be neglected). The percentage attack rate is worked out for each mouse, and these rates are then averaged to give three mean attack rates for each occasion of testing. Full biological details of the method will be published elsewhere by Mr. L. C. Stones.