A correlated morphological and cytochemical approach to the hemocytes in Leucophaea maderae characterizes the granule contents of blood cells with May Grunwald-Giemsa (MGG), periodic acid-Schiff (PAS), Alcian blue (AB), and Sudan black B stainings, and after fluorochroming with acridine orange (AO). The cell nucleus and nuclear DNA is demonstrated with the Feulgen reaction. The activities of α-naphtyl butyrate esterase (ANBE) and acid phosphatase (AcPase) have been investigated in hemocytes, by both light and electron microscopy. The study discloses five cells types: prohemocyts, plasmatocytes, granulocytes, spherulocytes, and cytocytes. Occasional Sudan black-positive cells could represent an adipohemocyte category. The different patterns of cytochemical staining suggest a variety of functional roles for hemocytes. The most selective reaction pattern in terms of cytological differentiation among hemocytes occurred with the ANBE reaction. Ultrastructural analysis of intercellular granule contents, and the demonstration of cells with intermediate features, suggests that the hemolymph of Leucophaea maderae contains a developmental series from prohemocyte to plasmatocyte to granulocyte and then to spherulocyte. © 1993 Wiley-Liss, Inc.