Experimental observations of food-aversive responses in larvae of Spodoptera exempta (Wlk.) (Lepidoptera, Noctuidae)

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Abstract
The oligophagy of the African armyworm S. exempta, was investigated experimentally. The resistance to feeding on cassava, a non-food plant, declined at a faster rate if the larvae had been reared on artificial diet. If diet-reared larvae were allowed to feed on maize for increasing periods of time the subsequent rejection of cassava increased accordingly. This effect could still be induced after removing the labral or palpal sensilla but not after removing both pairs of styloconic sensilla. The left and right pair of styloconic sensilla are supplementary to each other. In so far as aversive responses to non-food plants are concerned, the rearing on artificial diet can be considered as a case of pseudomaxillectomy. During feeding on maize the larva probably receives a specific input pattern which influences central acceptance-rejection decisions in a time-dependent manner. This specific information is absent fron the artificial diet and can no longer be perceived by larvae without styloconic sensilla.