Survival and reproductive output of Chironomus tentans (Diptera: Chironomidae) in response to parasitism by larval Unionicola foili (Acari: Unionicolidae).

Parasitic associations between larval Unionicola foili and the dipteran Chironomus tentans were established in the laboratory, and the effects of these water mite larvae on survival and reproduction of C. tentans were determined. Longevity of parasitized insects was not significantly different from those that were unparasitized. Furthermore, there was no significant difference in the onset of oviposition between parasitized and unparasitized female chironomids. However, infected females oviposited significantly more eggs compared to uninfected controls. This study contradicts others indicating that water mite larvae severely reduce the survivorship and reproductive output of insects. The results are consistent with analyses indicating that degree of parasitism is not correlated with either duration of the parasitic phase or longevity of larvae following their parasitic association with chironomids. Larval U. foili apparently secure sufficient nutritional resources to complete their development, yet their hosts still exhibit fitness components expected for unparasitized individuals. Extreme site specificity exhibited by larval U. foili may limit the degree of parasitism on host insects and in doing so preclude larval mites from achieving infection levels that could negatively impact host survival and reproduction.