Abstract. Imagoes of the dragonfly Coenagrion puella are parasitized frequently by ectoparasitic water mites. In an experimental study of the parasite load we examined the influence of parasite burden on host sperm volume. Infection with ectoparasitic water mites did not affect sperm volume in the seminal vesicle (ejaculate volume). It is concluded that water mite parasitism does not affect male fitness in C. puella by reducing sperm production.