The phylogeny of the fungus gnat tribe Exechiini (Diptera: Mycetophilidae) is reconstructed based on the combined analysis of five nuclear (18S, two parts of 28S, CAD, EF1α) and two mitochondrial (12S, COI) gene markers. According to known fossil record, and recent higher‐level phylogenies, the tribe constitutes the most apomorphic, distinctly monophyletic clade of the family Mycetophilidae. The tribe originated in the Paleogene and apparently quickly diversified in the Neogene with an unusual rapid radiation of complex male terminalia. Earlier attempts to reconstruct the phylogeny of the tribe, based on both morphology and molecular methods, have not yielded reliable hypotheses, neither in terms of resolution nor in terms of support for major clades. Increased taxon sampling and wider gene sampling have been suggested to achieve better phylogenetic resolution. Aiming at this, we present new phylogenies, for the first time with all known genera and subgenera of Exechiini represented. While many terminal intergeneric relationships are well supported, both in maximum likelihood and in Bayesian analyses, most of the major, deeper clades remain poorly supported. We suggest that a rapid radiation event close to the root may be causing the low resolution at this level in the phylogeny. This contrasts parallel phylogenies of the older subfamilies and tribes of the family Mycetophilidae, where traditional clades have usually been recovered with high support. Further in‐depth studies into the evolutionary history of the tribe are needed to enlighten and coalesce the specific phenomena driving their unique morphological, genetic and phylogeographic histories.

Exechia is a diverse genus of small fungus gnats, widespread in the Holarctic Region, while the fauna is largely unknown elsewhere, such as in the Afrotropical and Oriental Region. Members of Exechia can be arranged into several species groups, based on homologies in the male and female terminalia. The Exechia parva group is delimited, based on male terminalia possessing a pair of gonocoxal lobes on the apicoventral gonocoxal margin. Eight previously-described species can be placed in this group, of which six are from the Holarctic Region, while one is recorded each from the Oriental and the Afrotropical Regions. The Exechia parva group was reviewed and found to include 33 species, of which 24 were described as new to science and six were re-described. Identification keys to 32 species for males and nine species for females are provided together with illustrations and photos of male and female terminalia. Species delimitations were based on morphological examination of 94 male and female specimens, as well as DNA barcodes obtained from 124 specimens. Molecular and morphological species delimitations were mostly congruent, except in two cases where two species were delimited within a single Barcode Index Number (BIN). We found that each species is only known from a single zoogeographical region and that several species complexes are largely congruent with zoogeographical divisions, indicating that intercontinental barriers may have a strong impact on the species diversity of the group.

The small genus Coelophthinia Edwards, 1941 of the subfamily Gnoristinae (Diptera, Mycetophilidae) is so far known to harbour four species from the Palaearctic, Nearctic and Neotropical Regions. Extensive DNA barcoding of fungus gnats of the family Mycetophilidae through the International Barcode of Life project (iBOL) have initiated integrative studies resulting in taxonomic upgrades and a better understanding of many species and their delimitation. The opportunity was also taken to describe the mitogenome of a member of Coelophthinia for the first time. The integrative studies give evidence for splitting the European species C. thoracica Edwards, 1941 into three different species. Four new species are described from the USA, Japan and the Nordic Region in Europe, Coelophthinia cirra Kerr sp. n., Coelophthinia itoae Kurina sp. n., Coelophthinia lata Kjaerandsen sp. n. and Coelophthinia loraasi Kjaerandsen sp. n., raising the number of Holarctic species from two to six. The mitogenome of Coelophthinia loraasi sp. n. is described and analysed.