Feeding preferences and foraging in Larvae of Manduca sexta and Spodoptera littoralis : a laboratory study based on olfaction

Abstract: Larvae of Lepidopteran Manduca sexta and Spodoptera littoralis are pests of economical importance in several horticultural and agricultural crops. Knowledge of insect feeding preferences and behavior is crucial in order to find economically and ecologically sustainable solutions to the problems caused by these herbivores. The aim of this thesis was to study the behavior and the induced feeding preferences in larvae of M. sexta and S. littoralis when reared on certain host plants. The hypothesis was that larvae of M. sexta would have an innate preference for plants of the Solanaceae family and therefore discriminate the previously experienced nonhost when faced with the choice between a true host and the previous food source. S. littoralis where hypothesized to prefer the plants on which they previously have been feeding of. Larval dual choice tests were made in an olfactometer, testing the olfactorybased preference of larvae of M. sexta, reared on foliage of oilseed rape, tomato, potato or synthetic diet, and the olfactory- based preference of S. littoralis, reared on foliage of cowpea, cotton, cabbage or synthetic diet. Among the larvae of M. sexta, reared on foliage of potato, there was significant attraction to the prior experienced host while the larvae of S. littoralis preferred cabbage in all experiments, regardless of prior host. M. sexta reared on oilseed rape did not survive long enough to be tested.