Unveiling the feeding response of Spodoptera litura to natural host and artificial diet

Behavioral studies play a crucial role in assessing food utilization in insects. However, there exists a gap in our understanding of the phenotypic plasticity in Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) and how it impacts their growth, development, and potential for plant damage. This study aimed to investigate the phenotypic plasticity of S. litura, with a focus on its immature stages, and evaluate the consequences of plant damage and pest management. We conducted in vitro experiments using both a standard artificial diet and tobacco (Nicotiana tabacum L., Solanaceae) plants to assess the growth, development, survival, longevity, reproductive capacity, and egg-laying capability of S. litura larvae and adults. A type II functional response was estimated for all larval instars, utilizing the Likelihood Holling's Disk model, which provided two key coefficients: the search rate (a) and handling time (T_h). Our findings revealed that sixth instars exhibited exceptional agility and efficiency, requiring the shortest time to process each milligram of diet compared with other larval stages. Moreover, when larvae were fed on tobacco, they displayed the shortest developmental time and the highest fecundity. This trend extended to pupal weight, pupal duration, pupal emergence, fecundity, and longevity, which were all significantly higher in individuals fed on tobacco. Additionally, S. litura larvae that fed on tobacco exhibited greater efficiency in converting digested food and lower approximate digestibility compared to larvae fed the artificial diet. These results underscore the importance of focusing on the management of fourth, fifth, and sixth instars, which have the potential to cause severe plant damage. Understanding the functional and nutritional response of S. litura larvae enhances the efficiency of integrated pest management strategies (IPM) at early stages while minimizing ecological impact.