Killing house-flies, Musca domestica L., by means of hanging drops of insecticide.

Abstract

Basic laboratory investigations have been carried out on a method for giving house-flies, Musca domestica L., relatively large doses of insecticide, with a view to possible applications in controlling, or preventing the appearance of, resistant strains of flies. The principle is that a relatively large drop of mineral oil will hang on the lower end of a thin vertical or near-vertical wire (e.g., a drop of up to 3 μl. on a wire 0·3 mm. in diameter), and a fleeting contact of a fly with the drop will generally transfer to the surface of the fly a substantial volume of oil. For investigational purposes pins were inserted obliquely into rods (e.g., about 700 pins into a rod 60 cm. long), and drops of up to about 1 μl. were formed on the ends of the pins by dipping the pin-bearing rods into solutions of insecticide in oil. In a typical experiment a rod with suspended drops was hung vertically from the ceiling of a chamber into which flies were released; flies then collected doses of insecticide when attempting to alight on the rod.