The morphology of Hessian fly larval (first instar) midgut and salivary gland tissue is described by light and transmission electron microscopy. These data serve as the basis for future research aimed at understanding the mechanisms of wheat resistance to Hessian fly. Future studies include (1) a comparison of the midgut morphology of larvae that have fed on resistant vs. susceptible wheat cultivars and (2) the use of in situ hybridization in salivary gland tissue to determine the cytological location of gene transcripts putatively involved in conferring susceptibility of wheat plants to Hessian fly attack.