An Optimized Corn-Based Artificial Diet Reshapes the Larval Metabolome, Leading to Mixed Improvements in Longevity...

Spodoptera litura (Fabricius) is a major agricultural pest, and the establishment of efficient mass-rearing systems is critical for advancing biological control and integrated pest management strategies. In our previous work, evaluation of 17 artificial diets identified an optimised corn-based formulation (F15) that significantly improved larval performance relative to a standard control (CK) diet. However, the metabolic mechanisms underlying these performance differences remain largely unresolved. Here, we employed untargeted metabolomics based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) to elucidate the biochemical pathways associated with enhanced development in S. litura larvae reared on F15 compared with CK. Larvae fed the F15 diet exhibited a prolonged developmental period (21.49 ± 0.86 vs. 20.13 ± 0.53 days), higher emergence rates (1.20 ± 0.27% vs. 0.85 ± 0.10%), and increased body mass during both early (3.28 ± 0.12 vs. 2.93 ± 0.08 mg) and later instars (77.55 ± 2.30 vs. 73.51 ± 1.17 mg) relative to those reared on the control diet. Metabolomic profiling revealed that the CK diet, characterised by lower levels of the essential fatty acid linoleic acid (LA), was associated with reduced metabolite abundance and weaker enrichment of energy-related metabolic pathways. In contrast, the F15 diet contained substantially higher levels of linoleic acid, which is known to contribute to membrane stability and mitochondrial function. Notably, linoleic acid was consistently enriched in the gut of F15-fed larvae, suggesting a correlative central role in promoting metabolic efficiency, growth, and developmental performance. Collectively, these findings provide mechanistic insight into how dietary composition modulates insect metabolism and highlight the nutritional and physiological advantages of corn-based formulations for large-scale rearing. This study offers a foundational theoretical foundation for optimising artificial diets and supports their application in sustainable pest-management programs.