Effects of a mite, Limnochares americana (Hydrachnida: Limnocharidae), on the life-history traits and grooming behaviour of its damselfly host, Enallagma ebrium (Odonata: Coenagrionidae)

We examined whether experimental parasitism by a mite Limnochares americana (Lundblad) affected survivorship and maturation of adult damselflies Enallagma ebrium (Hagen). We then tested whether differences in grooming activity between control and exposed individuals (within different age or sex categories of host) mirrored reductions in fitness that resulted from experimental parasitism. We based our choice of experimental numbers of mites on our finding that adult damselflies had between 0 and 12 mites (71% had 0 mites), and mature adults had a higher prevalence and intensity of parasitism than did prereproductive damselflies in two of three field surveys. Low numbers of mites did not affect survivorship of teneral or mature males and females; however, high numbers of mites significantly depressed survivorship of teneral males and females and mature males, and were associated with a delay in maturation of females. Of teneral individuals, only females groomed more than controls when challenged with low numbers of mites; mature individuals of both sexes groomed more than controls in response to high numbers of mites but not in response to low numbers. Our results suggest that variation in grooming behaviour partially reflects variation in fitness costs, due to mite parasitism, across age and sex categories of hosts.