The binomial Chironomus (C.) savoreljela nom. nov. is proposed as replacement name for Chironomus inermifrons auct. (sensu Pinder, 1978) nec Goetghebuer, 1921

A modified and updated diagnosis of Parametriocnemus adult males is provided by examining 13 morphological characters to separate the genus from the other 32 genera of Orthocladiinae worldwide with macrotrichia on the wing membrane. Consequently, seven species assigned to Parametriocnemus are transferred to other genera. Parametriocnemus tenuiapicalis is recognized as a new species based on a description including drawings of a species from Turkey addressed as Parametriocnemus sp. in a publication by Caspers and Reiss 1989. A provisional identification key to the males of the 31 species of Parametriocnemus of the world is presented, assisted by a table containing data for 19 characters of each species. The shape of the hypopygium inferior volsella was found to be the most important character to distinguish species.

Male adults and pupae of the genus Lopescladius from the Nearctic are reviewed. The morphologies of adult male and pupal Lopescladius (Cordiella) hyporheicus Coffman and Roback, 1984, are reexamined and compared to the Neotropical Cordiella. The pupa of Lopescladius (Lopescladius) inermis Sӕther, 1983, is described, along with comments on the adult male. Three additional pupal morphotypes are described. Keys are included for adult males and pupal exuviae from the Nearctic. Large range expansions are reported for several species.

Washington State, USA has extensive coastal habitats that extend from marine or estuarine ecosystems upstream to the upper mixing zone where tidal surge and freshwater meet. We document a rare maritime chironomid genus, Eretmoptera Kellogg, 1900, from these habitats. The larvae of Eretmoptera were identified from 21 samples composed of 17 sites in the Puget Lowlands and Coast Range ecoregions based on a total of 1067 samples examined. Larvae were compared to reference material to confirm identification. We document Eretmoptera from low order forested streams in urban and private lands. Many sites sampled were near marine habitat and likely experienced saltwater intrusion while at least six sites were far from saltwater intrusion and were likely fully freshwater. We compare larval habitat for Eretmoptera in this study to larval habitat of the sub-Antarctic and Antarctic E. murphyi Schaeffer, 1914, the only species in the genus for which larvae have been associated. The georeferenced data provided in this study should spur further research to find and associate all life stages for Eretmoptera in Washington State to verify the genus identification and to help solve its taxonomic position within maritime and terrestrial Orthocladiinae.

Parakiefferiella ferringtoni sp. n., previously recorded as the provisional taxon Orthocladiinae Genus 5 sensu Coffman and Ferrington (2008), is described based on larval, pupal, pharate male and female material. This species resides in the Pacific Northwest region of the Nearctic. The morphology of P. ferringtoni sp. n. blurs the lines between genera of the Parakiefferiella group. We review the state of generic taxonomy of the Parakiefferiella group, with an emphasis on providing explicit morphological synapomorphies to delineate each genus, although Parakiefferiella Thienemann and Lappokiefferiella Tuiskunen have no unambiguous synapomorphies.

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Northern European Corynoneura species with the combination of comparatively short extension of the hind tibia apex and a thick transverse stern-apodeme are morphologically similar to species in Thienemanniella. Moreover, the generic placement of Corynoneurella paludosa Brundin has been debated. We present results from morphological and molecular analyses that clarify the taxonomy of C. paludosa. Consequently, we regard Corynoneurella as a junior synonym of Corynoneura, move Corynoneurella paludosa to Corynoneura and return Corynoneurella afra (Lehmann) to Thienemanniella. Our observations also conclude that Corynoneurella paludosa sensu Langton is morphologically different from C. paludosa (Brundin) and is best placed in Thienemanniella as Thienemanniella langtoni sp. n. Corynoneura ferringtoni sp. n. and Corynoneura minimagna sp. n. are described and diagnosed based on adult male morphology and DNA barcodes. We redescribe Corynoneura minuscula Brundin, discuss Corynoneura magna Brundin, and suggest a solution for the identity of Corynoneura celeripes Winnertz. Finally, we provide an identification key to adult males of Holarctic Corynoneura species with a short hind tibial extension.

Winter is typically viewed as a time when insects are thought to be inactive; however, some aquatic insects (e.g., chironomid flies, stoneflies, and mayflies) have species which complete multiple life stages and emerge as active, terrestrial adults during winter. These insects have adaptations that permit survival at low temperatures and are known to occur in seasonally cold environments worldwide. However, awareness and education around these specialized insects are lacking partially due to the limited research and education centered around winter aquatic ecology. The Bugs Below Zero project, started in 2019, aims to enhance awareness and increase appreciation for winter-adapted aquatic insects, providing opportunities for the public to engage in community science efforts collecting data on these insect groups. The program has received positive reception in classroom and outreach settings and has successfully provided multimedia educational materials to hundreds of educators and data collection opportunities to numerous volunteer groups and classrooms. With the help of volunteers, the Bugs Below Zero team aims to add to the body of scientific knowledge about winter active insects and to continue educating students and community members about these organisms, their role in food webs, and their conservation needs.

The Chironomidae are one of several groups of aquatic insects with representatives that possess cold hardening strategies that allow pronounced hibernal activity, including species that complete their life and reproduce only during the coldest months of the year. Although these winter-active species are often ignored in aquatic studies, relatively recent research has demonstrated that these insects are not only interesting, but they can also be an important and diverse element of aquatic insect communities. This review synthesizes existing literature on winter-emerging Chironomidae, focusing largely on Holarctic species emerging from temperate streams that are at least partially ice-free throughout the winter season. We found that there are currently at least 215 chironomid taxa present during winter, predominated by Orthocladiinae (n = 127), Chironominae (n = 42) and Diamesinae (n = 35). Our review highlights cold hardening strategies, such as supercooling, that permit winter activity, and we also discuss growth and emergence for species that have been extensively studied, such as Diamesa mendotae Muttkowski. Winter-active species tend to be long-lived at cold temperatures, and we discuss how consequences of climate change, including warmer temperatures and reduced snowpack, may negatively impact certain winter-active species. Although there is a growing base of studies featuring winter-active species, our review demonstrates that research is largely restricted to a handful of localities, and autecology studies are limited to only select species. We emphasize the importance of extending field work into the winter season and expanding research on winter Chironomidae to a broader geographic range to better gauge species accounts and enhance our understanding of the importance of winter-emerging Chironomidae.

Two strange species are described and illustrated here based on adult males collected from China and Malaysia respectively. The combination of conventional diagnostic character states is unusual in both species, and we cannot allocate either into any currently recognized genera. We propose that these represent two new genera in the tribe Chironomini. Here we adopt ‘Chironomini taxon 1’ and ‘taxon 2’ as coded unresolved names for further discussion.