Beyond growth: The impact of diet on body composition in the farmed cricket Gryllodes sigillatus.

The relative availability of macronutrients can shape industrially relevant traits of mass-reared insects, including their final nutrient composition. Gut-loading - temporarily enriching insects through their final meals - is widely used to enhance feeder insects for captive insectivores, yet it remains unclear whether nutrient composition reflects true assimilation or residual diet in the gut, and whether macronutrient gut-loading can enrich whole-body composition. We examined how diets with distinct protein to carbohydrate (P:C) ratios influence adult body composition and whether changes arise from assimilation or gut contents. We reared Gryllodes sigillatus (Walker) (Orthoptera: Gryllidae) on seven diets with different P:C ratios (8:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:8) and measured adult macromolecular composition (carbohydrates, proteins, and lipids) both with intact gut contents and after gut clearing. Crickets fed carbohydrate-rich diets had greater carbohydrate content and females had heavier guts, with carbohydrates largely assimilated into body tissues. In contrast, elevated protein levels in crickets fed protein-rich diets reflected both assimilation and gut-loading, with protein-rich diets driving higher lipid levels. These results clarify that macronutrient assimilation in crickets is diet and sex-dependent and inform strategies for manipulating edible insect nutritional profiles.