Water mite parasitism is associated with body condition and sex of the whirligig beetle Dineutus nigrior (Coleoptera: Gyrinidae)

Larval water mites parasitize a variety of aquatic insects and may have a negative impact on host fitness. Here we tested whether mite parasitism is associated with sex and body condition the whirligig beetle Dineutus nigrior (Coleoptera: Gyrinidae), a host where mite parasitism has not previously been reported. There was a pattern of higher mite intensity in males indicating that males were more heavily exposed or more susceptible to mite parasitism. However, there was not a consistent sex bias in mite prevalence. Host body condition was negatively correlated with mite abundance in both sexes. This could suggest that mite reduce host body condition and thus negatively impact host fitness. Alternatively, individuals in poor body condition may be more susceptible to mite parasitism, suggesting that there may be a condition-dependent mite resistance mechanism in this host.