Morphology of haemocytes of healthy and Beauveria bassiana (Bals.) Vuill.infected Dicladispa armigera (Olivier) adults was examined in a phase contrast microscope to characterize them into different types. The total haemocyte count (THC) and the differential haemocyte count (DHC) were also estimated. Four types of haemocytes were identified: prohaemocyte, plasmatocyte, granulocyte and spherulocyte. In the healthy adults, the THC varied between 5055 and 5950/mm 3 , out of which 85% were composed of granulocytes and plasmatocytes. As B. bassiana infection time increased, THC decreased and was associated with a significant concomitant increase in granulocytes and a decrease in prohaemocytes. Granulocytes reacted in various ways, including disintegration of the plasma membrane, formation of fine pseudopod-like cytoplasmic extensions and finally, clumping of cells. Granulocytes and plasmatocytes were the predominant haemocytes involved in all the cell-mediated defence reactions.