Parasitism and survival in a damselfly: does host sex matter?

We present experimental data on the survivorship of damselflies infested by parasitic water mites from a population in field cages. In addition, we sh ow correlative laboratory data under simulated severe weather conditions. I n the manipulative experiment, parasitized females' individual condition, w hich was measured as weight at emergence, was an important determinant of s urvival under field conditions. In contrast, such a relationship did not oc cur in males and unparasitized females. It was found in the laboratory expe riment that water mites as well as weight at emergence both contributed sig nificantly to the reduced survivorship of male and female damselflies. It w as concluded that the impact of parasitism depends on environmental conditi ons and that host sexes differ in their responses to parasitism. This is di scussed in the light of immunocompetence in invertebrates.