FEEDING ON NONHOST PLANTS BY PARTIALLY MAXILLECTOMIZED TOBACCO HORNWORMS (MANDUCA-SEXTA, LEPIDOPTERA, SPHINGIDAE)

Tobacco hornworm larvae reared on diet or jimsonweed and with one or both pairs of maxillary sensillae styloconica removed were given feeding tests with four non-host plants (collard, dandelion, cowpea and mullein). Increased feeding was observed for all larvae lacking medial, lateral, or both pairs of sensillae; these increases were greater for larvae that had been reared on jimsonweed. For larvae with both pairs of sensillae removed, all test plants were highly acceptable. For larvae with only the lateral sensillae removed, the test plants were only slightly more acceptable. Diet-reared larvae with the median sensillae removed found test plants slightly more acceptable than did control larvae. Jimsonweed larvae lacking only the median sensillae found dandelion, normally a rejected plant, almost completely acceptable. Possible physiological reasons for these behavior changes are discussed.