Mode of Action of Antifeeding Compounds in the Larvae of the Tobacco Cutworm, Spodoptera litura (F.) (Lepidoptera : Noctuidae) III. Sensory Responses of the Larval Chemoreceptors to Chlordimeform and Clerodin

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Abstract
Antifeeding activities of clerodin and chlordimeform in a topical application on the larval olfactory and various gustatory chemosensilla were studied. The morphological and histological characteristics of these chemosensilla of the tobacco cutworm are similar to those of other lepidopterous larvae. Clerodin produced antifeeding activity and slight excitation symptoms when it was applied to the sensilla basiconica of the apical segments of both maxillary palps; chlordimeform produced antifeeding activity and extreme excitation symptoms when it was applied to the hypopharynx. Chlordimeform''s obvious excitation symptoms were hyperactivity in locomotion with several rubbing trials of the mouth parts on the filter paper and biting trials to the thoracic legs, followed by uncoordinated movements as a result of tremors beginning in the mandibles and maxillae and in the thoracic legs later. The proposed primary site of action of clerodin is the maxillary palps. The primary site of action of chlordimeform is the hypopharynx.