Ultrastructural comparison of the larval midguts of Plodia interpunctella (Hübner, 1813) and Pyralis farinalis (Linnaeus, 1758) (Lepidoptera: Pyralidae)

Both Plodia interpunctella and Pyralis farinalis belong to Pyralidae (Lepidoptera) and are economically significant stored-product pests, yet they differ in both external morphology and biological habits. The larval midguts of the two confamilial larvae were compared using light microscopy (LM) and transmission electron microscopy (TEM), to explore potential links between midgut ultrastructure and biological habits. The midgut is a tubular structure with relatively uniform diameter in both species. The epithelium is composed of digestive, goblet, and regenerative cells. Notably, the regenerative cells exhibit two distinct distribution patterns: distributed individually and aggregated to form regenerative nidi. In P. interpunctella , the rough endoplasmic reticulum of digestive cells is concentrated in the apical region, while in P. farinalis it is distributed around the nucleus and at intercellular junctions. Glycogen aggregations are present in the digestive cells of P. farinalis , but are absent in P. interpunctella . Some goblet cells are situated at the base of the epithelium and display basal infoldings, forming a basal plasma membrane with multiple openings in P. interpunctella . In contrast, the basal region of P. farinalis goblet cells lacks such features. The goblet cells of P. interpunctella possess numerous deep infoldings of the basal labyrinth, implying a more prominent role in ion regulation and water transport.