Sympistis zetterstedtii. The Arctic and Subarctic species Sympistis zetterstedtii was treated as a northern subspecies of Sympistis nigrita, which occurs in central Europe by Ronkay and Ronkay (1995). Sympistis nigrita zetterstedtii occurs across northern Eurasia and into northwestern North America.<br><br>Sympistis zetterstedtii kolthoffi. Troubridge 2008 followed Franclemont and Todd 1983 in treating the taxon S. labradoris (Staudinger, 1901) as a subspecies, but under the species S. nigrita instead of S. zetterstedtii. He then treated S. kolthoffi (Aurivillius, 1890) and S. besla (Skinner and Mengel, 1891) as new synonyms of subspecies zetterstedtii. For those wishing to recognize subspecies, zetterstedtii is primarily an Old World taxon with an entirely dark hindwing. It occurs in North America in Alaska and Yukon, but intergrades with the North American form, which has the basal two-thirds of the hind wing pale, in southern Yukon. At the subspecific level, kolthoffi is the oldest available name for the North American form, so labradoris and besla should be synonymized under Sympistis nigrita kolthoffi.<br><br>Sympistis besla, S. labradoris. These taxa are synonyms of S. zetterstedtii at the species level and synonyms of S. kolthoffi at the subspecies level.
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      <li>Mikkola K, Lafontaine JD, Kononenko VS (1991) Zoogeography of Holarctic species of Noctuidae (Lepidoptera): importance of the Beringian Refuge. Entomologica Fennica 2: 1-17.</li>
      <li>Franclemont JG, Todd EL (1983) Noctuidae. pp. 120-159. In: Hodges et al. (1983).</li>
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