PATTERNS OF WATER MITE PARASITISM IN MINNESOTA DRAGONFLIES BASED ON MUSEUM COLLECTIONS.

T.M. Anderson. Division of Science and Math, University of Minnesota-Morris, Morris, MN 56267

Water mite larvae (Acari: Hydrachnidia) commonly parasitize adult dragonflies, though these associations are not often studied. To investigate the occurrence of these parasites on dragonflies in Minnesota I examined 2581 specimens representing 78 species from the University of Minnesota Insect Collection. Water mites occurred on 28 species but on only 11% of individuals. Over 95% of the mites were Arrenurus spp. though Limnochares americana were also observed. Mites rarely occurred on Cordulegastridae, Gomphidae, Aeshnidae or Corduliinae, where 0-4 % of individuals were infested. Mites occurred more frequently on Libellulinae, in which 18 of 28 species and 17% of individuals were parasitized. Over 30% of the specimens of Celithemis eponina, Leucorrhinia hudsonica, L. intacta, Sympetrum internum, and S. rubicundulum had mites. Over 50% of infested dragonflies had 10 or fewer mites, while only 4% had more than 100 mites. Mite infestation levels differed significantly from the Poisson distribution suggesting that dragonflies may differ in their susceptibility to attack by water mites. While museum collections do not necessarily mimic natural populations, they can provide baseline information on the extent of water mite parasitism in the Odonata and help generate testable hypotheses about the potential impact of water mites on their hosts.