Published online by Cambridge University Press: 10 July 2009
(1) Spraying of huts with 0·1 per cent. pyrethrum in kerosene, at the rate of 25 c.c. per 1,000 cubic feet, deterred 90 per cent. of A. minimus from entry on the following night. The repellent effect persisted in diminished degree for at least four days.
(2) A rather larger quantity of pyrethrum, sprayed in a Freon aerosol, produced a similar but somewhat less marked effect.
(3) The repellent effects of Lethane 384 in kerosene were much less marked, and not discernible on the second night.
(4) Different species varied greatly in their sensitivity to the repellents.
(5) Two types of repellent effects were indicated. Repellent effects proper were the most important, and males were more sensitive to these than females of the same species. There was also a masking effect, to which anthropophilic females were sensitive, which resulted from obscuring of attractive human scents by the chemical odours.