More than any other group of macro-organisms, true flies (Diptera) dominate the freshwater environment. Nearly one-third of all flies—roughly 46,000 species—have some developmental connection with an aquatic environment. Their abundance, ubiquity, and diversity of adaptations to the aquatic environment position them as major drivers of ecosystem processes and as sources of products and bioinspiration for the benefit of human society. Larval flies are well represented as ecosystem engineers and keystone species that alter the abiotic and biotic environments through activities such as burrowing, grazing, suspension feeding, and predation. The enormous populations sometimes achieved by aquatic flies can provide the sole or major dietary component for other organisms. Harnessing the services of aquatic Diptera for human benefit depends on the ingenuity of the scientific community. Aquatic flies have played a role as indicators of water quality from the earliest years of bioassessment. They serve as indicators of historical and future ecological and climate change. As predators and herbivores, they can serve as biological control agents. The association of flies with animal carcasses in aquatic environments provides an additional set of tools for forensic science. The extremophilic attributes of numerous species of Diptera offer solutions for human adaptation to harsh terrestrial and extraterrestrial environments. The potential pharmaceutical and industrial applications of the symbiotic microbial community in extremophilic Diptera are better explored than are those of dipteran chemistry. Many flies provide valuable ecological and human services as aquatic immatures, but are also pests and vectors of disease agents as terrestrial adults. The scientific community, thus, is challenged with balancing the benefits and costs of aquatic Diptera, while maintaining sustainable populations as more species face extinction.

Assessing the biodiversity of macroinvertebrate fauna in freshwater ecosystems is an essential component of both basic ecological inquiry and applied ecological assessments. Aspects of taxonomic diversity and composition in freshwater communities are widely used to quantify water quality and measure the efficacy of remediation and restoration efforts. The accuracy and precision of biodiversity assessments based on standard morphological identifications are often limited by taxonomic resolution and sample size. Morphologically based identifications are laborious and costly, significantly constraining the sample sizes that can be processed. We suggest that the development of an assay platform based on DNA signatures will increase the precision and ease of quantifying biodiversity in freshwater ecosystems. Advances in this area will be particularly relevant for benthic and planktonic invertebrates, which are often monitored by regulatory agencies. Adopting a genetic assessment platform will alleviate some of the current limitations to biodiversity assessment strategies. We discuss the benefits and challenges associated with DNA-based assessments and the methods that are currently available. As recent advances in microarray and next-generation sequencing technologies will facilitate a transition to DNA-based assessment approaches, future research efforts should focus on methods for data collection, assay platform development, establishing linkages between DNA signatures and well-resolved taxonomies, and bioinformatics.

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 phylogenetic relationship between the two extant subfamilies of Ptychopteridae is examined using morphological characters. Bittacomorphinae is supported as a monophyletic group with several synapomorphies. Monophyly of the Ptychopterinae is less certain. Descriptions are provided for the family and subfamilies. The genera and species of Bittacomorphinae are reviewed, and phylogenetic relationships within the subfamily are discussed. While Bittacomorpha is a monophyletic group, Bittacomorphella is probably paraphyletic. Redescriptions of the species of Bittacomorpha and most of Bittacomorphella are presented. Bittacomorphella furcata sp. nov, is described from the central Coast Range of Oregon and Olympic Peninsula of Washington, USA. The range of Bittacomorphinae is found to extend into the Neotropical region with a record of Bittacomorpha clavipes from Costa Rica. A key to the world species of Bittacomorphinae is provided. Printed copy of this book is available from US$25.8 plus postage, Click here to order.

Neoderus Alexander, 1927 (Diptera: Tanyderidae) is revised to include a new species, Neoderus chonos Madriz, sp. n. Adults of N. chonos were collected in January 2016 from two sites in Chilean Patagonia. This paper provides a description of the new species, including the first male description of the genus, diagnosis of adult Neoderus, and redescription of N. patagonicus (Alexander, 1913). Habitat characteristics, known distribution and historical information for the new species are also discussed. A generic key to adults of world Tanyderidae is given. urn:lsid:zoobank.org:pub:27F176EE-57EE-4427-BD97-521FA4C92D68