Drawings of erythrocytic stages of Haemoproteus syrnii in the blood of Strix aluco. 1–4: young trophozoites with an initial volutin granule; 5: two young gametocytes with 1 or 2 volutin granules attached to the initial granule; 6–7 young gametocytes; 8–10 mature macrogametocytes; 11, 13: mature microgametocytes; 12: old microgametocyte; 14: two microgametocytes within the same RBC; 15: a microgametocyte spread beneath the RBC nucleus; 16: microgametocyte with faded staining and where the volutin granules are still visible.