The Bombyx mori silkworm is very important econom- ically and is a model for several studies. The larval life of silkworms is divided into five instars. The 5th instar is the longest, where the larvae show maximum food consumption and growth. The silk is produced in a paired gland composed of glandular epithelium and a lumen. Food digestion occurs in the midgut, represented by a folded columnar monolayered epithelium, which includes goblet cells and stem cells in a basal lamina. We aimed to investigate the influence of concentrations of iron oxide nanoparticles (IONPs) in food on the silk gland and midgut morphology.