EFFECTS OF LARVAL DIET AND LARVAL AGE ON THE RESPONSIVENESS OF TASTE NEURONS OF SPODOPTERA-LITTORALIS TO SUCROSE

Previous experiments with a bean-based artificial diet have shown that the responsiveness of peripheral sensilla of larvae of Spodoptera littoralis to sucrose is influenced by the age of the larvae within a stadium. This paper investigates that effect with another artificial diet (wheat-based) and with plant material from two host plants, cabbage and seedling wheat. The present results show that the three diets influence the responsiveness of neurones to sucrose and sodium chloride. The effects of the diets on the day-to-day responses and the within-day responses to both stimuli are illustrated. The neural response of the lateral maxillary styloconic sensillum to sucrose correlates with larval weight during the first 3 days of the final stadium, but no comparable relationship was found with sodium chloride, suggesting that different mechanisms operate for different stimuli. The mechanisms which may be involved in the day-to-day changes in neural responses to sucrose are discussed.