A combination of light and electron microscopy were used to examine the fine structure of the alimentary tract of the root feeding New Zealand grass grub, Costelytra zealandica. The short foregut region contained a small cuticle-lined crop surrounded by a well-defined musculature. The large midgut region was differentiated into the anterior and posterior regions by two series of gastric caeca. Both regions of the midgut contained specialized zones of columnar cells that appeared to undergo apocrine secretion. Throughout the length of this tissue, a well-developed peritrophic membrane was formed. Parasitic gregarines were detected frequently in the ectoperitrophic space. The lack of musculature in this tissue suggested that the food bolus was moved through the food tract by the action of the hindgut muscles pulling on the peritrophic membrane. The cuticle-lined hindgut could be differentiated into a fermentation sac containing arbiforous cuticlar projections that harboured a complex array of microbes and a rectal region surrounded by a distinct cryptonephridial complex.