Efficacy of the Fenitrothion Microcapsule against Termites, Coptotermes formosanus SHIRAKI (Isoptera : Rhinotermitidae). : II. Transmissibility of Fenitrothion through Grooming

The effect of a microcapsule formulation of organophosphorus insecticide, fenitrothion, on workers and soldiers of Coptotermes formosanus SHIRAKI (Rhinotermitidae) was further investigated. Untreated workers as well as treated ones died (or became moribund) in the presence of workers or soldiers that had been sprayed with a water-diluted microcapsule solution, indicating the transmission of poison between individuals. In all conditions, soldiers showed much less sensitivity to the microcapsule formulation than workers. Self and mutual-grooming by workers was noted to be critical to microcapsule efficacy, resulting in the transmission of insecticide from poison-donors (insecticide-contaminated individuals) to poison-recipients (workers). Bioassay of microcapsule-treated soil for the efficacy against mouth-obturated and deantennated workers showed that poisoning of workers was delayed compared with that of unoperated ones. This result supports the assumption of the importance of transmission in the poisoning process. The basis of the transmission of the present fenitrothion microcapsule among termite workers is dependent on adhesion of microcapsules to the appendages, especially to the antennae, followed by self- and mutual-grooming. Grooming results in the breakage of microcapsules and oral intake of the active ingredient of the formulation by the groomers, as well as dermal intake by those that are groomed.