AbstractEighteen species are listed of which eight are described as new. Most of these species were collected in the more southerly parts of the Canadian Arctic, but two species were collected at Lake Hazen which is situated in the extreme northeastern portion of Ellesmere Island. The majority of the species belong to well known Holarctic genera. Characteristically Palaearctic groups are represented by five species, but exclusively Nearctic groups are represented by a single species. The most conspicuous biological feature is the apparent reversal of the switch mechanism governing the production of sexuales since, in spite of the excessively long photoperiod, oviparae are common.