Look into L.G. Van der Starre- Van der Molen Neth J zool 22: 119-182 1972; Neth J. Zool 22: 183-206 1972 and Z. Zellforsch 125:295-305 1972. The Z.Zellforsch gives in the article a second author W de Priester. I don't have his publications at hand, but check because he did a lot on insect gut Light and electr microscopy. Succes.