Adaptive sex ratio theory explains why gametocyte sex ratios are female-biased in many populations of api-complexan parasites such as Plasmodium, and Toxoplasma. Recently, Ferguson has criticized this framework and proposed two alternative explanations - one for vector-borne parasites (e.g. Plasmodium) and one for Toxoplasma. Ferguson raises some interesting issues that certainly deserve more empirical attention. However, it should be pointed out that: (1) there are theoretical and empirical problems for his alternative hypotheses; and (2) existing empirical data support the application of sex ratio theory to these parasites, not its rejection.