We celebrate Raymond J. Gagné for his contributions to taxonomy of the Mycetophilidae (Diptera), specifically for his forty-one-years-old monograph of Holarctic Trichonta Winnertz, 1864 that is still the primary source used for species identification in the genus. We briefly reflect on his monograph's impact and demonstrate by use of recent DNA barcode data extracted from BOLD Systems (BOLD) that the model for the distribution of Holarctic Mycetophilidae that Gagné presented in the monograph still holds up to scrutiny. To demonstrate the refined species concept now being applied by use of an integrative taxonomic approach that includes DNA barcodes, we revise a small, but distinct, species complex that Gagné recognized as one morphologically defined species and used as an example of an old pan-Holarctic taxon, Trichonta vulcani (Dziedzicki, 1889). We find the Trichonta vulcani species complex (sensu Kallweit 1998) to consist of at least six species in the Holarctic Region of which three are being described as new to science: Trichonta japonica Kurina, new species (East Palearctic), Trichonta neovulcani Kjaerandsen, new species (East Nearctic), Trichonta raymondgagnei Kjaerandsen, new species (Holarctic), Trichonta trifida Lundstrom, 1909 (wide Palearctic), Trichonta tristis (Strobl, 1898) (wide Palearctic), and Trichonta vulcani (Dziedzicki, 1889) (wide Palearctic). All six species are distinctly separated by DNA barcodes that correspond well to minor, but constant, differences in their male terminalia. However, one of the widespread species, Trichonta trifida, displays some genetic and morphological differentiation between western and eastern Palaearctic populations. We presently consider these populations conspecific pending broader sampling. We further propose a replacement name Trichonta nepalensis Kjaerandsen, new name for Trichonta superba Gagné, 1981, a junior primary homonym of Trichonta superba Ostroverkhova, 1979, the latter being a junior secondary synonym of Trichonta tristis (Strobl, 1898).

Five genera of the mycophagous subfamily Porricondylinae are reported for the first time to occur in New Zealand, namely Asynapta, Camptomyia, Colomyia, Divellepidosis, and Paratetraneuromyia. New species in these genera, all to be attributed to both authors, are described and named Asynapta bicornis, Camptomyia rakiura, Colomyia inexpectata, Divellepidosis constricta, D. eximia, D. tewaipounamu, Paratetraneuromyia denticulata, and P. multidenticulata. The genus Yukawaepidosis, previously monotypic and ill-defined, is shown to have a second, previously unnamed species, which is described as Y. kaikoura and compared with Y. aliculata (Yukawa). The generic definition of Yukawaepidosis is revised. All species descriptions are based on the morphology of males caught in flight (i.e., Nothing is known on the habitat and biology of the larvae.). Altogether, New Zealand's Porricondylinae are now known to comprise 33 species in eight genera, representing all the three tribes recognized in this subfamily, namely Asynaptini, Dicerurini and Porricondylini.

A new species of gall midge, Gagnemyia alstoniae Adair and Kolesik, is described from flower bud galls on milkwood tree Alstonia actinophylla (A. Cunn.) K. Schum. in far northern Australia. Galled flower buds fail to open and set seed. Larva, pupa, male, and female of the new species are described and illustrated. A new genus, Gagnemyia Adair and Kolesik, is proposed to contain the new species. Gagnemyia is tentatively placed in the tribe Clinodiplosini and is characterised by a robust aedeagus bearing asetose sensilla, an undivided male hypoproct that is wrapped around the aedeagus, a needle-like ovipositor, toothed tarsal claws and larval terminus bearing two pairs of corniform and two pairs of setiform papillae. This is the first record for Cecidomyiidae feeding on Apocynaceae in Australia.

Macrolabis molesta Dorchin, new species damaging young shoots of commercially grown spineless butcher's broom (Ruscus hypophyllum L.) in Israel is described based on adults, larvae and pupae. Larvae develop gregariously in growing shoots, causing distortion and rotting of the apical meristem, thus rendering affected shoots unsuitable for marketing. This is the first Macrolabis species to be recorded from a monocotyledonous plant. It completes at least one generation a year in fall and early winter, sometimes with an additional generation in spring. Macrolabis molesta has not been detected on the native butcher's broom, R. aculeatus L., thus it may have been introduced into Israel with its host plant in the early 20^th century.

Two new species of gall midges (Diptera: Cecidomyiidae: Cecidomyiinae) associated with male flower buds of Phyllanthus flexuosus (Phyllanthaceae) are described and illustrated. Clinodiplosis gagnei Elsayed, new species, induces male flower bud galls, whereas Macrolabis katoi Elsayed, new species, is an inquiline. Females of both species visit the host plant at flowering in search of suitable oviposition sites and, in doing so, become dusted with pollen of the opened male flowers and come in contact with the stigmas of female flowers. Larvae of both gall midge species overwinter in the ground, and each has only one generation per year. This is the first report of the genus Macrolabis in Japan.

We analyzed the Folmer fragment of the mitochondrial COI gene of three closely related species of Semudobia (Diptera: Cecidomyiidae): S. betulae (Winnertz), S. tarda Roskam, and S. skuhravae Roskam. These species form fruit galls on different birch species (Betula, Betulaceae) in the Holarctic Region. In Japan, larvae of S. betulae and S. tarda were collected from the native Japanese birch, B. platyphylla, whereas S. skuhravae was collected from the eastern Palearctic birch, B. ermanii. In the Netherlands, the three species were collected from intermediate forms between the Eurasian endemic birches, B. pendula and B. pubescens. Additional sequences of Canadian and European S. betulae and S. skuhravae were obtained from the Barcode of Life Data system (BOLD). In a maximum likelihood analysis, the individuals of each species formed strongly supported clades, but genetic divergence was high within each clade indicating species complexes. European and Canadian individuals of S. betulae and S. skuhravae each formed a single clade with low intraspecific variation, suggesting that these species were introduced together with their hosts to North America. In contrast, Japanese individuals of the three Semudobia species were remarkably distant from European and Canadian individuals, indicating that they have been isolated genetically for a long period on their native eastern Palearctic and Japanese hosts.

Stomatosematidi are by far the smallest of the four supertribes of Cecidomyiinae (Diptera: Cecidomyiidae) containing 56 species. The life history of only one species has been known previously: adults of Stomatosema nemorum Kieffer were reared from larvae feeding on a mushroom, Lactarius sp. (Fungi: Russulaceae). Here we describe the larva and adults of a new species, Stomatosema gagnei Kolesik, that was found inducing pustulate leaf galls on Causonis trifolia (Vitaceae) plants in Cape York Peninsula, Australia. Stomatosema gagnei is the first Stomatosematidi with a described larva and the first known to cause a gall. The fact that a species of Stomatosematidi, a supertribe hypothesized to be the sister group to all remaining Cecidomyiinae, was found inducing a plant gall suggests that the first of the transitions from the ancestral fungus-feeding habit to plant-feeding occurred in Cecidomyiidae at the base of the Cecidomyiinae clade more than 100–110 million years ago, during the lower Cretaceous.

The genus Vitisiella (Diptera: Cecidomyiidae) is newly recorded from Japan, and Vitisiella gagnei So, Elsayed, and Tokuda, new species, which induces subglobular leaf galls on Vitis vinifera (Vitaceae) in Hokkaido, is described as new to science. The new species is distinguishable from its congeners by the combination of the following morphological features: undivided mediobasal lobes in male terminalia, ovipositor ca. 2.5 times as long as tergite VII, and larval six terminal papillae placed ventrally. We provide a fragment of the Cytochrome Oxidase subunit I (COI) mitochondrial gene sequence and report the life history and phylogenetic information for the new species.

The genus Hercostomoides Meuffels and Grootaert (Diptera: Dolichopodidae: Sympycninae) is revised and now comprises seven species. The type species, Hercostomoides indonesianus (Hollis) is now regarded as a junior synonym of Campsicnemus rufinus Frey, new synonym in the combination Hercostomoides rufinus (Frey), new combination. This species is widespread, ranging from the tropical Orient to Korea, and also Australia. Other species include Hercostomoides bhartii Grichanov and H. wauensis, new species, both from New Guinea, H. flavipleurus, new species, H. baroalba, new species, and H. gagnei, new species, all from Australia, and H. yapensis, new species from the Yap Islands and Guam. The generic definition of Hercostomoides is revised to comprise Sympycninae that have femur III without a strong anterior preapical seta, dorsal setae present on the antennal scape, and whose females have a tectiform clypeus.

Records of Diptera and their hymenopteran parasitoids are reported from a ten-year study of herbivorous insects of Nantucket Island, Massachusetts, USA, with a focus on searching for galls, leaf mines, and other characteristic feeding evidence on host plants. Our field observations and reared specimens are supplemented with herbarium records and Johnson's (1930) list of the insect fauna of Nantucket. Compared with Johnson's list of nine species of Agromyzidae, we identified 53 along with 15 others determined only to genus or higher taxa (a few of the latter could conceivably be conspecific with the former or with one another). We found 37 named species of Cecidomyiidae (including eight of the nine on Johnson's list), as well as 26 others that are undescribed or are currently unidentifiable for other reasons (a few of which could conceivably be conspecific with one of the identified species, or represent galls not actually caused by midges). A few rearings and collections of Anthomyiidae, Chloropidae, Ephydridae, Phoridae, Sphaeroceridae, and Tephritidae are reported, adding another seven species and two genera to Johnson's list. Cerodontha (Dizygomyza) edithae Eiseman and Lonsdale (Agromyzidae), an as yet undescribed species of Ophiomyia Braschnikov (Agromyzidae), Megaselia nantucketensis Eiseman and Hartop (Phoridae), and the cecidomyiid parasitoids Platygaster tephrosiae Buhl and Eiseman and P. vitisiellae Buhl and Eiseman (Hymenoptera: Platygastridae) are known only from specimens reared as part of this study, which also produced paratypes of Liriomyza pistilla Lonsdale (Agromyzidae). Noteworthy cecidomyiid records include the first known specimens of an undescribed Asphondylia Loew on Solidago sempervirens L. (Asteraceae), galls of an undetermined lasiopterid species on Tephrosia virginiana (L.) Pers. (Fabaceae) that have only been found on Nantucket, and previously unreported galls on Gaylussacia baccata (Wangenh.) K. Koch (Ericaceae), Ionactis linariifolia (L.) Greene (Asteraceae) (Dasineura Rondani sp.), Quercus prinoides Willd. (Fagaceae), Salix purpurea L. (Salicaceae), and Solidago latissimifolia Mill. (Asteraceae) (Asphondylia sp., Rhopalomyia Rübsaamen sp.).

Described as new are 12 species of snail-killing flies (Diptera: Sciomyzidae) of the genus Dictya Meigen from the Americas: D. ahbellae, D. aprilae, D. coryi, D. dunnei, D. emrehorum, D. garlandi, D. gibbsi, D. heyjimi, D. jemae, D. jofusi, D. malloyi, and D. youngi. Specimens representing these species were discovered among more than 5600 specimens of Dictya examined by the author between 2007 and 2022. The 12 new species bring to 56 the number of described, valid species in the genus Dictya. Also identified and described for the first time is the female of D. praecipua Orth.

We describe the egg, three instars, and pupa of Dacus bivittatus Bigot using optical and scanning electron microscopy and compare them with those of other Dacus Fabricius species for which these stages have been described as well as those of two important pest species of Zeugodacus Hendel that infest cucurbits. A new anatomical term, lateral lips, is introduced to describe a feature of the facial mask. A feature of the egg that has not been reported previously for Tephritidae is described here: a peculiar arrangement of aeropyles in an irregular line partially encircling the egg near the posterior end. A table of morphological characters visible with light microscopes provides diagnostic information to separate larvae of Dacus bivittatus from those of most other Dacus species and two Zeugodacus species for which larvae have been described.

Subpelignus Papp is revised, including description of (1) a new species, S. gagnei Zatwarnicki and Mathis (New Zealand. North Island. ND: Whananaki South (35°31.1′S, 174°27.2′E); (2) two new combinations, Subpelignus antennalis (Aldrich, 1931) and Subpelignus limosinus (Becker, 1896); (3) a new synonym, S. hortobagensis Papp, 1983 = S. limosinus Becker; and (4) description of a new subgenus, Niratissa Zatwarnicki and Mathis, for S. maculipennis Mathis and Zatwarnicki. Descriptions of revised and the newly described species include some of the first illustrations of structures of the male terminalia. Detailed locality data for all species examined are provided. For perspective and to facilitate genus-group and species-group recognition, the tribe Atissini is diagnosed and a key to included genera is provided.

Onycholyda raymondi Smith, new species, Pamphilius gagnei Smith, new species, and P. murrayi Smith, new species, all from the eastern United States, are described, illustrated, and separated from related species.