We present a summary and analysis of the Diptera-related information published in Zootaxa from 2001 to 2020, with a focus on taxonomic papers. Altogether, 2,527 papers on Diptera were published, including 2,032 taxonomic papers and 1,931 papers containing new nomenclatural acts, equivalent to 22% of all publications with new nomenclatural acts for Diptera. The new nomenclatural acts include 7,431 new species, 277 new genera, 2,003 new synonymies, and 1,617 new combinations. A breakdown by family of new taxa and new replacement names proposed in the journal during the last two decades is provided, together with a comparison of Zootaxa’s output to that of all other taxonomic publications on Diptera. Our results show that the journal has contributed to 20% of all biodiversity discovery in this megadiverse insect order over the last 20 years, and to about 31% in the last decade.

The systematics of the dipteran family Sciaridae is based mainly on morphological characters and has remained quite controversial. In this study, we used two mitochondrial DNA markers (CO1, 16S) and a nuclear one (28S) to take a glimpse into phylogenetic relationships of part of the North and Central European Sciaridae. A total of 91 species from 19 genera were analysed using Maximum Likelihood based phylogenetics (depending on the availability of valid sequences, 50–70 per gene). We strengthen the suggestion of the Chaetosciara group as an independent subfamily. Within the subfamily Megalosphyinae, two separate Bradysia clades were identified, suggesting a close relation between the genera Zygoneura, Austrosciara, and Scatopsciara. The genus Alpinosciara gen. n. is established to place the species of the former Corynoptera crassistylata group inside the subfamily Megalosphyinae. This new genus now includes 22 species.

The known insect associates of Caltha palustris L. (Ranunculaceae) in North America are reviewed. Zygoneura calthella new species (Sciaridae) is described from western Massachusetts, USA. Larvae bore in petioles and stems of C. palustris and mine into the basal portions of the leaves. DNA barcodes of the new and other Zygoneura species are presented. Inquilines and parasitoids in the larval galleries of Z. calthella include an undescribed species of Elachiptera Macquart (Chloropidae); Megaselia limburgensis (Schmitz) (Phoridae); Scaptomyza pallida (Zetterstedt) (Drosophilidae); and a species of Neurateles Ratzeburg (Ichneumonidae). Larvae of Prasocuris boreella (Schaeffer) (Chrysomelidae) feed externally on foliage of the same plants.

A new species of the genus Ctenosciara Tuomikoski, 1960 is here described based upon a single specimen, obtained from collectings in the garden at Museum Alexander Koenig in Bonn. Ctenosciara alexanderkoenigisp. n. differs from all other congeneric European species by its striking coloration and distinct male genitalia. However, DNA barcoding reveals associations with two specimens from New Zealand. Therefore a recent migration of Ctenosciara species from the Australasian Region, the likely center of origin of the genus, is discussed. A key to the European species of Ctenosciara is provided. Barcoding results reveale that Ctenosciara exigua is not clearly distinguished from Ctenosciara hyalipennis by its COI sequence (both share the same BIN BOLD:AAH3983) and that its species status may be questionable.

Phytosciara greylockensis, new species (Sciaridae), is described from Mt. Greylock in western Massachusetts, USA. Larvae are initially leafminers on Clintonia borealis (Aiton) Raf. (Liliaceae), later feeding on leaves externally. DNA barcodes of the new and most other Phytosciara species are presented.

Review of the genus Cratyna Winnertz (Diptera: Sciaridae) in Korea, including the description of a new species