Gametocyte sex ratios (proportion male) of mixed vs. single clone infections compared with the corresponding haematocrit (r ed b lood c ell density) measured on the same day of infection. Each individual infection was measured daily for both these parameters until either the host died or the infection was cleared by the host (thus until the peak of infection). Infections were initiated by injection of 106 parasites for single clone treatments and 5 × 105 of each clone in mixed infections. Thai clone (squares); SL clone (open circles); mixed clones (crosses). Circled cross represents one individual that had a high sex ratio associated with a high density of reticulocytes on one particular day (see text).