Abstract
Multiparasitism by different species of larval water mites was observed on an adult midge collected in Hokkaido, northern Japan. Water mite larvae of Hygrobates sp. and Unionicola sp. in an inactive stage were discovered from a single chironomid female in the subfamily Chironominae. Eight Hygrobates larvae parasitized on the dorsum, and four were on the venter from the first to fourth abdominal segments of the midge. One Unionicola larvae attached on the trochanter of the left midleg and one on the femur of the right midleg. Their attachment sites on the midge accorded well with the larval site preferences of these two genera, as reported in past studies. Considering the preference of Unionicola for the specific segments of the legs, the observed site partitioning between Hygrobates and Unionicola seems to have originated by intrinsic site preferences of each taxon rather than interspecific competition. On the other hand, two less-engorged Hygrobates larvae were observed among the fully engorged larvae on the abdominal segments of the midge. Such developmental variations are possibly caused by intraspecific competition for nutrients among conspecific larvae on a single host individual.
