Abstract: In the course of cage tests with 666 baits against nymphs of the migra tory locust Locusta migratoria manilensis Meyen),it has beetle stlggested that fumigation action of 666 might be responsible for parts of the knockdowns of nymphs which had not tasted the bait．A review of literature reveals that fmnigation action of 666 had been demonstrable againstmany species of insect exclusive of the migratory locust. Experiments were therefore carried out in September,1950 on the fumigation of 666 agaiinst this particular pest.