Larval host plant experience modulates both mate finding and oviposition choice in a moth

Host plant choice in polyphagous insects can be connected with costs of being naïve when confronted with several potential host plants, for example through slower decision making. Utilization of earlier experience could be one way to overcome some of these limitations. We studied whether larval feeding experience influences mate finding by males and female choice of oviposition site in the moth Spodoptera littoralis. Larvae were reared on either artificial diet or the host plants, cotton, clover or alfalfa, and we recorded the behaviour of adults from each diet. In two sets of experiments, in both the laboratory and the field, we investigated the female's oviposition choice and the male's response to female pheromone with different plant odour backgrounds. We found that experience with cotton, clover or alfalfa during the larval period induced female oviposition on the corresponding plant both in the laboratory and in the field. Furthermore, males were more attracted to female sex pheromone combined with odour from a host plant species that they had experienced as larvae than to sex pheromone combined with odour from host plant species they had not experienced. The results show convergent modulation of male and female responses to plant odour depending on their larval food plant. The influence of larval experience during the first-to-fifth instars on host preference was also stronger than the influence of experience acquired in the late larval, pupal and early adult stages. Consequences for host plant choice efficiency and fitness effects for males and females are discussed.