In haemolymph of fifth and sixth instar larvae, prepupae and pupae of the cabbage moth, Mamestra brassicae, five haemocyte types were identified, viz. prohaemocytes, plasmatocytes (standard and nematoform), granulocytes, spherulocytes and oenocytoids. Considerable developmental changes in the differential and total haemocyte counts were observed. Greatest change in the number and proportion of cell types occurred just before pupation and in the early pupal stage. Study of phagocytic activity of haemocytes showed phagocytic rates of 17.1, 52.8, 39.2 and 41.2 % in Coxiella burnetii phase I, C. burnetii phase II, latex beads and iron saccharate, respectively. The main phagocytic cells were granulocytes and plasmatocytes.