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The paper provides new information on morphological characters which are useful in generic diagnostics of the Proisotoma complex of Isotomidae. Based on this information, a number of known species are excluded from the redefined Proisotoma s. str. and moved to the genus Scutisotoma Bagnall, 1949, which is again given generic status. The following genera are given more precise definitions: Subisotoma Stach, 1947, Ballistura Börner, 1906, Proisotoma Börner, 1901 and Weberacantha Christiansen, 1951. A new genus, Strenzketoma, is erected for the species “Proisotoma” buddenbrocki Strenzke. Scutisotoma titusi (Folsom), S. muriphila (Grinbergs), and S. ladaki (Denis) are redescribed. Fourteen new species of the genus Scutisotoma (S. acorrelata sp.n., S. baica sp.n., S. dodecocellata sp.n., S. indigirka sp.n., S. karadagi sp.n., S. kolymica sp.n., S. longisensilla sp.n., S. matalini sp.n., S. millimetrica sp.n., S. montana sp.n., S. nicksmeti sp.n., S. schisti sp.n., S. stachanoremi sp.n., S. tenuidentifera sp.n.) and two new species of Weberacantha (W. echinodermata sp.n., W. magnomucrella sp.n.) are described. Types of S. ananevae (Babenko & Bulavintsev), S. armeriae (Fjellberg), S. christianseni (Stach), S. oirota (Vilkamaa), S. stepposa (Martynova), S. tianshanica (Martynova), and S. tolerans (Babenko) have been studied. Keys to genera and to the known Holarctic species of Scutisotoma Bagnall and Weberacantha Christiansen are given.

Soil life supports the functioning and biodiversity of terrestrial ecosystems. Springtails (Collembola) are among the most abundant soil arthropods regulating soil fertility and flow of energy through above- and belowground food webs. However, the global distribution of springtail diversity and density, and how these relate to energy fluxes remains unknown. Here, using a global dataset representing 2470 sites, we estimate the total soil springtail biomass at 27.5 megatons carbon, which is threefold higher than wild terrestrial vertebrates, and record peak densities up to 2 million individuals per square meter in the tundra. Despite a 20-fold biomass difference between the tundra and the tropics, springtail energy use (community metabolism) remains similar across the latitudinal gradient, owing to the changes in temperature with latitude. Neither springtail density nor community metabolism is predicted by local species richness, which is high in the tropics, but comparably high in some temperate forests and even tundra. Changes in springtail activity may emerge from latitudinal gradients in temperature, predation and resource limitation in soil communities. Contrasting relationships of biomass, diversity and activity of springtail communities with temperature suggest that climate warming will alter fundamental soil biodiversity metrics in different directions, potentially restructuring terrestrial food webs and affecting soil functioning.

The available literature data on the species diversity and geographical distribution of Collembola in Canada and Alaska is summarized. In total, the checklist covers 541 named species of Collembola. This includes 475 species in 135 genera from 24 families recorded from Canada, as well as 241 species in 75 genera from 19 families reported from Alaska. For each species the current name, basionym with a full reference, records for different provinces and territories with their authorships, and general distributional ranges are given. Taxonomic remarks have been added when necessary. The checklist is based on 536 references (including 262 with Canadian records) published up to May 2018 and on a number of publicly available online resources.