Morphological Ontogeny and Ecology of a Common Peatland Mite, <i>Nanhermannia coronata</i> (Acari, Oribatida, Nanhermanniidae)

<i>Nanhermannia coronata</i> Berlese, 1913, is a common and abundant oribatid species in peatlands but can be easily mistaken for <i>N</i>. <i>sellnicki</i> Forsslund, 1958, as an adult. Therefore, the identity of adults of <i>N</i>. <i>coronata</i> from several sites in Norway and Ireland was supported by the COI sequence data, and based on this material, the morphological ontogeny of this species is described and illustrated to highlight the differences between <i>N</i>. <i>coronata</i> and <i>N</i>. <i>sellnicki</i>. In all juvenile stages of <i>N</i>. <i>coronata</i>, the bothridial seta is absent, but two pairs of exobothridial setae are present, including short <i>exp</i> and <i>exa</i> reduced to its alveolus. In the larva, seta <i>f</i>₁ is setiform, but in the nymphs, it is reduced to its alveolus. Most prodorsal and gastronotal setae of larva are short, and of nymphs they are long. In all instars, the leg segments are oval in cross section and relatively thick, and many setae on tarsi are relatively short, thick and conical, except for longer apical setae. Seta <i>d</i> accompanies solenidion σ on all genua, φ₁ on tibia I and φ on other tibiae. We found some morphological characters that clearly differentiate <i>N</i>. <i>coronata</i> from <i>N</i>. <i>sellnicki</i>, like the number of setae on femora of adults and tritonymphs, the shape of insertions of prodorsal seta <i>in</i> and all gastronotal and adanal setae of juveniles; in <i>N</i>. <i>sellnicki</i>, these setae are inserted in small individual depressions, whereas in <i>N. coronata</i>, these depressions are absent. Our ecological observations confirm a common occurrence of <i>N. coronata</i> in raised bogs, a high percentage of juvenile stages in its populations and a preference of this species for humid microhabitats, whereas <i>N</i>. <i>sellnicki</i> is less common than <i>N</i>. <i>coronata</i> and occurs in drier habitats.