The collection of spray droplets by flying locusts

Abstract

An account is given of work carried out since that of Wootten & Sawyer (1954) on the pick-up of spray droplets by flying locusts. The same species,Schistocerca gregaria(Forsk.), was used. The values given in their work for the amounts of spray collected were confirmed, but when observations were extended to cover smaller droplets (less than 50-μ. diameter), locusts were found to collect these much less efficiently.Other factors affecting pick-up were sex (females collected more spray than males) and flying speed (faster-flying locusts tended to collect less spray per unit of distance flown). When the angle of approach of the droplets to the flying locusts was varied between 1 and 11° from the horizontal no difference in the pick-up of spray could be detected.For droplets between 60- and 300-μ diameter, the dose of insecticide collected by the locusts is given by the formula 9xPC μg. for males, and 11·5xPC for females, when the locusts fly through a concentration of spray ofCml. per cu. m. for a distancePm. and the spray solution containsxper cent, (w/v) of insecticide.