An assessment of the efficiency of this composition gave the following results :- Initial BHC BHC BHC not BHC.not content recovered vaporized Efficiency vaporized (s .I (S.) (6.) (mmn) 9', 121.8 83-7 85.4 1.4 69.8 1'2
Entomological efficiency of insecticidal smoke generators
While the purpose of this paper is primarily to describe the development of insecticidal smoke generators, it is appropriate to mention here very briefly the effects of these smokes on insects. This subject will be discussed in more detail elsewhere.
Theoretically, the dispersion of an insecticide as a smoke should be particularly suitable for the disinfestation of inaccessible localities, such as lofts, thatched roofs, the holds of ships, jungle undergrowth, etc., especially in circumstances in which an immediate kill is sought, and not a sustained residual effect. It is also possible that the functioning of generators, if successful, would be quicker, and conservative of labour in the general disinfestation of dwelling houses,. greenhouses, warehouses, etc. The entomological efficiency is difficult to assess with accuracy, but trials have shown that DDT and benzene hexachforide smokes have an immediate killing effect on flies, mosquitoes, and other insects found in dwelling houses and farm buildings.
The residual effect has not yet been fully investigated. In one experiment, it was found that treatment of the kitchens at an R.A.F. station with insecticidal smoke caused a considerable reduction in both the house-fly and cockroach Fopulation for 2-3 months. Preliminary trials performed in jungle areas indicated that benzene hexachloride smoke was more effective against mosquitoes than was DDT smoke, while it has recently been reported that both hive been found effective against the tsetse fly.3 DDT and benzene hexachloride smoke generators also function satisfactorily under water, and they thus form a convenient means of producing a larvicidal film on the surface of mosquito-breeding pools. Trials have shown that DDT and benzene hexachloride are equally effective in this respect. A trial has recently been performed in a village church whose rafters had been attacked by the furniture beetle, Anobirim pirrrctatritrr. While it is too early to assess the effectiveness of the treatment, it has nevertheless been observed that the deposition of powdered wacd has ceased.
The above selection does not exhaust the trials which have been carried out with insecticidal smokes, but indicates the possibilities of success in this field.
The greater part of the analytical work involved in this investigation was performed by Miss M. V. Liddell.