Single male Enallagma ebrium were significantly and consistently parasitized by more larval water mites (Arrenurus spp. and Limnochares americana) than were males caught either in tandem or copula with females. Male size was inconsistently related to short-term mating success, although there was a consistent negative correlation between male size and mite numbers. Heavily-parasitized males responded less often to the presence of male models, and took significantly more foraging trips, than did lightly-parasitized males. Short-term mating biases with respect to ectoparasitism for E. ebrium males appears to result from reductions in competitiveness of heavily-parasitized males for access to females. Apparent reductions in competitiveness reflect decisions by heavily-parasitized males to pursue mating tactics which are energetically inexpensive. -from Author