Ants from samples from ten sap fluxes and rotten wood accumulations were examined for the presence of nematodes. The arboreal ant, Lasius brunneus, was found in seven of the ten samples. In the heads of L. brunneus five nematode species were detected: Koerneria histophora, Diploscapter sp., Oscheius dolichurus, Diplogasteroides spengelii and Halicephalobus similigaster, the latter two species for the first time in ants. The occurrence of Koerneria histophora more frequently than described in the literature can be explained by its strong preference for sap fluxes and rotten wood. It is hypothesised that only ants which come into contact with sap flux or rotten wood carry K. histophora. Waving dauer juveniles of Diploscapter sp. and H. similigaster successfully infested not only ants, but also beetles (Tenebrio molitor) in controlled experiments. In two of 11 cases, a transfer of dauer juveniles between ant specimens by trophallaxis was observed. Diploscapter sp. and H. similigaster left infested ants when they were stored in a wet environment.

The black fungus gnats Bradysia similigibbosa sp. n. and B. irwini sp. n. are described and new records of species of Bradysia Winnertz, Ctenosciara Tuomikoski, Epidapus Haliday, Pseudolycoriella Menzel & Mohrig, and Scatopsciara Edwards are presented for New Caledonia. A checklist of the sciarids of New Caledonia is given.

In the course of the present study 28 species of the genus Pseudolycoriella Menzel & Mohrig, 1998 from New Zealand were described as new to science: Pseudolycoriella aotearoa sp. n., Psl. dagae sp. n., Psl. dentitegmenta sp. n., Psl. fiordlandia sp. n., Psl. gonotegmenta sp. n., Psl. hauta sp. n., Psl. huttoni sp. n., Psl. jaschhofi sp. n., Psl. jejunella sp. n., Psl. kaikoura sp. n., Psl. maddisoni sp. n., Psl. mahanga sp. n., Psl. nahenahe sp. n., Psl. orite sp. n., Psl. plicitegmenta sp. n., Psl. porehu sp. n., Psl. porotaka sp. n., Psl. puhihi sp. n., Psl. raki sp. n., Psl. robustotegmenta sp. n.,Psl. subtilitegmenta sp. n., Psl. sudhausi sp. n., Psl. teo sp. n., Psl. tewaipounamu sp. n., Psl. tuakana sp. n., Psl. wernermohrigi sp. n., Psl. whakahara sp. n., and Psl. whena sp. n. Pseudolycoriella cavatica (Skuse, 1888), a widely distributed species, was recorded from New Zealand for the first time, and recognised as a senior synonym of Spathobdella setigera Hardy, 1960 syn. n. Apart from Psl. kaikoura and Psl. cavatica all New Zealand Pseudolycoriella species group in four different clusters: the Psl. bispina complex, the Psl. jejuna complex, the Psl. macrotegmenta complex, and the Psl. zealandica complex. The monophyly of those four species complexes was confirmed by a genetic analysis based on two mitochondrial genes (COI and 16S) and one nuclear gene (28S). A key to the species is given.

(1) We document the invertebrate fauna collected from 24 oak canopies in east and west Norway as a contribution to the Norwegian Biodiversity Information Centre’s ‘The Norwegian Taxonomy Initiative’. (2) A snap-shot inventory of the canopies was recorded by means of emitting a mist of natural pyrethrum into the canopies at night using a petrol-driven fogger and collecting the specimens in butterfly nets spread on the ground under the canopy. (3) Almost the entire catch of more than 6800 specimens was identified to 722 species. Out of 92 species new to the Norwegian fauna, 21 were new to science and, additionally, 15 were new to the Nordic fauna. Diptera alone constituted nearly half of the species represented, with 61 new records (18 new species). Additionally, 24 Hymenoptera (one new species), six oribatid mites (two new species) and one Thysanoptera were new to the Norwegian fauna. (4) Our study emphasizes the importance of the oak tree as a habitat both for a specific fauna and occasional visitors, and it demonstrates that the canopy fogging technique is an efficient way to find the ‘hidden fauna’ of Norwegian forests. The low number of red listed species found reflects how poor the Norwegian insect fauna is still studied. Moreover, the implication of the IUCN red list criteria for newly described or newly observed species is discussed.

Black Fungus Gnats (Sciaridae) are a megadiverse, cosmopoliltan family of bibionomorph Diptera. Even in Europe, the continent with the longest tradition in sciarid taxonomy, numerous taxonomic issues remain unresolved and countless species await discovery and description. The fauna of Norway is in these respects no exception. Recognising considerable knowledge gaps, the Norwegian Biodiversity Information Centre provided substantial funding for a detailed inventory of the Sciaridae species occurring in Norway, which was realised in 2014–2018. The results of this project will be published in a series of papers, of which the first is presented here, summarising available data on the taxonomy, faunistics, and autecology of Norwegian Sciaridae beginning with Zetterstedt’s pioneering work in 1838 and ending with 31 December 2019 as the cut-off date. All published records from that period were analysed. The result is a list of 143 species and four unplaced names. Following a consistent scheme, verified locality details are provide including alternative spellings, habitats, and flight times of adults in Norway, literature citations for the faunistic records, and general taxonomic references for classification or identification. A checklist of the sciarid fauna of Norway and a complete list of the relevant literature are also presented.