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We present a review and taxonomic update of the Macaronesian species of the muscid genera Phaonia and Muscina. As a preamble we argue that Phaonia tuguriorum (Scopoli) should be considered as a senior synonym of P. scutellata (Zetterstedt) (syn. nov.) and that the name P. signata (Meigen) (sp. rev.) is reestablished as the valid name for P. tuguriorum auctt. The Azores, Canary Islands and Madeira each have three species of Phaonia and three species of Muscina. One species and three subspecies are endemic to the Canary Islands: Phaonia nigrisquama Stein, P. tuguriorum canariensis Villeneuve (stat. nov.), P. trimaculata sordidisquama Stein (stat. nov.), and Muscina prolapsa fuscisquama ssp. nov. Identification keys to males and females are given for both genera.

The small Andean genus Myopella Malloch with two included species, M. angustifrons Malloch and M. appendiculata (Stein), is re-examined with special attention to the morphology of the male and female abdomen and terminalia. Adult morphology corroborates the current position of Myopella as an Andean endemic genus of Anthomyiidae, but its position within the anthomyiid tree remains in doubt despite the newly attained morphological knowledge. The status of the name Myopinella Michelsen, as proposed recently to replace for the preoccupied name Myopella Malloch, is clarified.

The Macaronesian species of the muscid genus Helina are revised. The genus is represented in the Canary Islands by 9 species, in Madeira by 7 species, and in the Azores Islands by 1 species. Four species, one divided in two subspecies, are endemic to the Canary Islands: Helina grancanariae sp. nov. (Gran Canaria), H. obscurisquama obscurisquama (Stein) (Tenerife, La Gomera), H. obscurisquama pseudonivalis (Santos Abréu) ssp. rev. (La Palma), H. rufitibialis Hennig (Tenerife, La Gomera, La Palma) and H. santosabreui sp. nov. (La Gomera, La Palma). The following three species are endemic to Madeira: Helina atlantica (Tiensuu), H. lundbladi Tiensuu and H. vilissima Hennig. Existing records of Helina almeriensis (Strobl) and H. quadrum (Fabricius) from the Canary Islands are considered as misidentifications. An identification key to males and females concludes the species accounts. Finally, a description is given of the previously unknown male sex of the endemic Madeiran Spilogona maderensis Michelsen.

Two new species from the genus Strongwellsea (Entomophthorales: Entomophthoraceae) that infect adult flies from the genus Helina (Muscidae) are described: Strongwellsea selandia Eilenberg & Humber infecting adult Helina evecta (Harris), and Strongwellsea gefion Eilenberg & Humber infecting adult Helina reversio (Harris). The descriptions are based on pathobiological, phenotypical and genotypical characters. The new species differ from other described members from the genus Strongwellsea by a) pathobiology as revealed by natural host species, b) morphology of primary conidia, c) color of resting spores, and d) genotypical clustering based on analysis of ITS2. The two new species have only been documented from North Zealand, Denmark., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

In mountain ecosystems, climate change can cause spatiotemporal shifts, impacting the composition of communities and altering fundamental biotic interactions, such as those involving flower-visiting arthropods. On of the main problems in assessing the effects of climate change on arthropods in these environments is the lack of baseline data. In particular, the arthropod communities on early flowering high-altitude plants are poorly investigated, although the early season is a critical moment for possible mismatches. In this study, we characterised the flower-visiting arthropod community on the early flowering high-altitude Alpine plant, Androsace brevis (Primulaceae). In addition, we tested the effect of abiotic factors (temperature and wind speed) and other variables (time, i.e., hour of the day, and number of flowers per plant) on the occurrence, abundance, and diversity of this community. A. brevis is a vulnerable endemic species growing in the Central Alps above 2000 m asl and flowering for a very short period immediately after snowmelt, thus representing a possible focal plant for arthropods in this particular moment of the season. Diptera and Hymenoptera were the main flower visitors, and three major features of the community emerged: an evident predominance of anthomyiid flies among Diptera, a rare presence of bees, and a relevant share of parasitoid wasps. Temperature and time (hour of the day), but not wind speed and number of flowers per plant, affected the flower visitors' activity. Our study contributes to (1) defining the composition of high-altitude Alpine flower-visiting arthropod communities in the early season, (2) establishing how these communities are affected by environmental variables, and (3) setting the stage for future evaluation of climate change effects on flower-visiting arthropods in high-altitude environments in the early season.

A new species from the genus Strongwellsea (Entomophthorales: Entomophthoraceae) is described: Strongwellsea crypta Eilenberg & Humber from adult Botanophila fugax (Meigen) (Diptera: Anthomyiidae). The description is based on pathobiological, phenotypical and genotypical characters. The abdominal holes in infected hosts develop rapidly and become strikingly large and edgy, almost rhomboid in shape. The new species S. crypta differs from S. castrans, the only described species infecting flies from Anthomyiidae, by: (a) naturally infecting another host species, (b) by having significantly longer primary conidia, and (c) by genotypical clustering separately from that species when sequencing ITS2., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

The Macaronesian species of the muscid genus Limnophora are reviewed with special emphasis on the fauna of the western Canary Islands. The genus is represented by 14 species in the Macaronesian archipelagos, with 10 species in the Canary Islands, 4 species in the Cape Verde Islands, and 3 species in Madeira. Limnophora obsignatula sp. nov. is endemic to the western Canary Islands, where it replaces the widespread continental L. obsignata (Rondani). It is further shown that L. paneliusi Emden, a species so far considered endemic to the Cape Verde Islands, is widespread in the Canary Islands. Two species, L. obsignata (Rondani) and L. tigrina Am Stein, are removed from the list of Canarian Muscidae as based on misidentifications of other species with a mesonotal "Anthomyia-pattern". Limnophora (Calliophrys) riparia capoverdica Emden, a taxon described from the Cape Verde Islands, is synonymized with L. riparia (Fallén), syn. nov. Distribution data and illustrated diagnoses are given for each species. The species account is finalized with an identification key to males and females. An assessment of the ovipositor as a characters source in phylogeny and species recognition is made for 12 species of Limnophora. Finally, it is pointed out that several species are acutely threatened due to habitat disturbance.

The occurrence of the muscid genus Spilogona Schnabl in Macaronesia is documented for the first time by the description of two new species, S. azorensis sp. nov. and S. maderensis sp. nov. These appear to be local endemics of the Azores and Madeira, respectively.

Two new species from the genus Strongwellsea (Entomophthorales: Entomophthoraceae) are described: Strongwellsea tigrinae from adult Coenosia tigrina (Diptera: Muscidae) and Strongwellsea acerosa from adult Coenosia testacea. The descriptions are based on pathobiological, phenotypical and genotypical characters. Further, the circumscription of the genus Strongwellsea is emended. Our findings suggest that Strongwellsea harbors a high number of species, of which now only five have been described., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Scouring-rushes (Equisetum sg. Hippochaete) are a group of horsetails with perennial aerial shoots strongly encrusted in silica. Accordingly, they seem to resist attacks from most herbivorous insects. Michelsen (2008) speculated that larval development of the European Pegomya terminalis (Rondani) and related anthomyiids takes place in specific scouring-rushes. Presently, we document that the larvae of two North American species related to P. terminalis attack developing shoots of Common scouring-rush, Equisetum hyemale L. Both species, Pegomya disticha Griffiths and P. cedrica Huckett, were found to coexist in a population of scouring-rush in Oklahoma. Various aspects of the life-history and morphology (3rd instar larva, male and female adults) for both species are described and documented by photos.

An account is given on the three species of the muscid genus Hebecnema Schnabl occurring in the Macaronesian islands. These are Hebecnema anthracina Stein from Madeira, H. anthracinella sp. nov. from the western Canary Islands, and H. fumosa (Meigen) found in the Canary Islands, Madeira and Azores. Existing Macaronesian records of H. umbratica (Meigen) from the Azores and H. vespertina (Fallén) from the Canary Islands are based on misidentifications. Diagnoses of the European species with photos of the male terminalia and a key to species are given. It is pointed out that the two species of Muscidae recently described as new from Sweden, Mydaea forsslundi Zielke, 2017 and Hebecnema brodina Zielke, 2018, represent exotic species, probably of Oriental provenance. Finally, morphological differences in the female ovipositor divide the seven European species of Hebecnema in two species groups.

Drapetis is a genus of tiny predaceous hybotid flies found frequently on the bark of trees. From a single locality in province Skåne (S Sweden) we report the co-existence of seven species of Drapetis. One is new and described as D. abrollensis sp. nov., and four species, D. assimilis (Fallén), D. completa Kovalev, D. infitialis Collin and D. stackelbergi Kovalev, are relatively recent additions to the list of Swedish Diptera. A key to males of the 14 species of Drapetis known from NW Europe is given. Special emphasis is given to modifications of the midleg cuticle observed in males of several species that belong to the D. exilis-species group. As shown by SEM images these modifications differ greatly between the species, both at light microscopic and ultrastructural levels. These modifications are introduced as a new set of characters in the identification key. Finally, brochosomes were detected on the midleg of three SEM-examined Drapetis species, documenting indirectly that small leafhoppers are regularly used as prey.

Study of all flies (Diptera) collected for one year from a four-hectare (150 x 266 meter) patch of cloud forest at 1,600 meters above sea level at Zurquí de Moravia, San José Province, Costa Rica (hereafter referred to as Zurquí), revealed an astounding 4,332 species. This amounts to more than half the number of named species of flies for all of Central America. Specimens were collected with two Malaise traps running continuously and with a wide array of supplementary collecting methods for three days of each month. All morphospecies from all 73 families recorded were fully curated by technicians before submission to an international team of 59 taxonomic experts for identification.        Overall, a Malaise trap on the forest edge captured 1,988 species or 51% of all collected dipteran taxa (other than of Phoridae, subsampled only from this and one other Malaise trap). A Malaise trap in the forest sampled 906 species. Of other sampling methods, the combination of four other Malaise traps and an intercept trap, aerial/hand collecting, 10 emergence traps, and four CDC light traps added the greatest number of species to our inventory. This complement of sampling methods was an effective combination for retrieving substantial numbers of species of Diptera. Comparison of select sampling methods (considering 3,487 species of non-phorid Diptera) provided further details regarding how many species were sampled by various methods.        Comparison of species numbers from each of two permanent Malaise traps from Zurquí with those of single Malaise traps at each of Tapantí and Las Alturas, 40 and 180 km distant from Zurquí respectively, suggested significant species turnover. Comparison of the greater number of species collected in all traps from Zurquí did not markedly change the degree of similarity between the three sites, although the actual number of species shared did increase.        Comparisons of the total number of named and unnamed species of Diptera from four hectares at Zurquí is equivalent to 51% of all flies named from Central America, greater than all the named fly fauna of Colombia, equivalent to 14% of named Neotropical species and equal to about 2.7% of all named Diptera worldwide. Clearly the number of species of Diptera in tropical regions has been severely underestimated and the actual number may surpass the number of species of Coleoptera.        Various published extrapolations from limited data to estimate total numbers of species of larger taxonomic categories (e.g., Hexapoda, Arthropoda, Eukaryota, etc.) are highly questionable, and certainly will remain uncertain until we have more exhaustive surveys of all and diverse taxa (like Diptera) from multiple tropical sites.        Morphological characterization of species in inventories provides identifications placed in the context of taxonomy, phylogeny, form, and ecology. DNA barcoding species is a valuable tool to estimate species numbers but used alone fails to provide a broader context for the species identified.

Estimations of tropical insect diversity generally suffer from lack of known groups or faunas against which extrapolations can be made, and have seriously underestimated the diversity of some taxa. Here we report the intensive inventory of a four-hectare tropical cloud forest in Costa Rica for one year, which yielded 4332 species of Diptera, providing the first verifiable basis for diversity of a major group of insects at a single site in the tropics. In total 73 families were present, all of which were studied to the species level, providing potentially complete coverage of all families of the order likely to be present at the site. Even so, extrapolations based on our data indicate that with further sampling, the actual total for the site could be closer to 8000 species. Efforts to completely sample a site, although resource-intensive and time-consuming, are needed to better ground estimations of world biodiversity based on limited sampling., Competing Interests: The authors declare no competing interests.

A new monotypic genus, Tapantiomyia gen. nov., is proposed for a new species of muscid fly, T. enigmatica sp. nov., found in the Tapantí National Park, Costa Rica. It is only known by a single male specimen taken in a Malaise trap in tropical cloud forest, but deserves immediate attention because of its bizarre, stilt-legged appearance in combination with several other unique apomorphies that preclude placement in any known genus of Muscidae. Tapantiomyia enigmatica is so strange that it tend to run out to Scathophagidae rather than Muscidae in keys to families of Diptera. However, the morphology of the male genitalia provides decisive evidence for a placement in Coenosiinae, a large and diverse group of predatory Muscidae. Two tribes, Limnophorini and Coenosiini, are currently recognized within Coenosiinae, but the monophyly of Limnophorini remains uncertain. Tapantiomyia is tentatively assigned to the Limnophorini.

DNA sequences offer powerful tools for describing the members and interactions of natural communities. In this study, we establish the to-date most comprehensive library of DNA barcodes for a terrestrial site, including all known macroscopic animals and vascular plants of an intensively studied area of the High Arctic, the Zackenberg Valley in Northeast Greenland. To demonstrate its utility, we apply the library to identify nearly 20 000 arthropod individuals from two Malaise traps, each operated for two summers. Drawing on this material, we estimate the coverage of previous morphology-based species inventories, derive a snapshot of faunal turnover in space and time and describe the abundance and phenology of species in the rapidly changing arctic environment. Overall, 403 terrestrial animal and 160 vascular plant species were recorded by morphology-based techniques. DNA barcodes (CO1) offered high resolution in discriminating among the local animal taxa, with 92% of morphologically distinguishable taxa assigned to unique Barcode Index Numbers (BINs) and 93% to monophyletic clusters. For vascular plants, resolution was lower, with 54% of species forming monophyletic clusters based on barcode regions rbcLa and ITS2. Malaise catches revealed 122 BINs not detected by previous sampling and DNA barcoding. The insect community was dominated by a few highly abundant taxa. Even closely related taxa differed in phenology, emphasizing the need for species-level resolution when describing ongoing shifts in arctic communities and ecosystems. The DNA barcode library now established for Zackenberg offers new scope for such explorations, and for the detailed dissection of interspecific interactions throughout the community., (© 2015 John Wiley & Sons Ltd.)

A taxonomic review of the European species of the Pegomya fulgens, furva and tabida species groups is given with emphasis on characters of importance for the identification of males and females. These Pegomya species groups are represented in Europe by two, two and nine species, respectively. Their mycophagous larvae may all feed exclusively on bolete sporocarps of Leccinum and Boletus aff. edulis. Their relationships and biology are summarized. Each species is given a selective list of references and synonymy, richly illustrated descriptions of males and females, a list or summary of the examined material, and a synopsis of the known distribution and biology. Pegomya ringdahli sp. nov., previously confused with P. scapularis (Zetterstedt, 1846), is described from Fennoscandia. Lectotypes are designated for Anthomyia fulgens Meigen, 1826 and Pegomyia (Pegomyia) furva Ringdahl, 1938. An identification key is given to all 17 species (males and females) of Pegomya that supposedly feed as larvae on sporocarps of Boletaceae and Suillaceae in Europe.

Fauna Europaea provides a public web-service with an index of scientific names (including important synonyms) of all extant multicellular European terrestrial and freshwater animals and their geographical distribution at the level of countries and major islands (east of the Urals and excluding the Caucasus region). The Fauna Europaea project comprises about 230,000 taxonomic names, including 130,000 accepted species and 14,000 accepted subspecies, which is much more than the originally projected number of 100,000 species. Fauna Europaea represents a huge effort by more than 400 contributing taxonomic specialists throughout Europe and is a unique (standard) reference suitable for many user communities in science, government, industry, nature conservation and education. The Diptera-Brachycera is one of the 58 Fauna Europaea major taxonomic groups, and data have been compiled by a network of 55 specialists. Within the two-winged insects (Diptera), the Brachycera constitute a monophyletic group, which is generally given rank of suborder. The Brachycera may be classified into the probably paraphyletic 'lower brachyceran grade' and the monophyletic Eremoneura. The latter contains the Empidoidea, the Apystomyioidea with a single Nearctic species, and the Cyclorrhapha, which in turn is divided into the paraphyletic 'aschizan grade' and the monophyletic Schizophora. The latter is traditionally divided into the paraphyletic 'acalyptrate grade' and the monophyletic Calyptratae. Our knowledge of the European fauna of Diptera-Brachycera varies tremendously among families, from the reasonably well known hoverflies (Syrphidae) to the extremely poorly known scuttle flies (Phoridae). There has been a steady growth in our knowledge of European Diptera for the last two centuries, with no apparent slow down, but there is a shift towards a larger fraction of the new species being found among the families of the nematoceran grade (lower Diptera), which due to a larger number of small-sized species may be considered as taxonomically more challenging. Most of Europe is highly industrialised and has a high human population density, and the more fertile habitats are extensively cultivated. This has undoubtedly increased the extinction risk for numerous species of brachyceran flies, yet with the recent re-discovery of Thyreophoracynophila (Panzer), there are no known cases of extinction at a European level. However, few national Red Lists have extensive information on Diptera. For the Diptera-Brachycera, data from 96 families containing 11,751 species are included in this paper.

The present catalogue of Anthomyiidae attempts to list all species (173) described or recorded from mainland China (165) and Taiwan (8) that for various reasons are not treated in "Flies of China" from 1998. The catalogue further lists Chinese species that are presently standing in new generic combinations compared to those of "Flies of China", species that have changed name because of synonymy or misidentification, and species upgraded from subspecies to species. Regional distribution by province is specified for all species. Literature sources to descriptions or records of anthomyiid species from China are only given for those 173 species not covered by "Flies of China". Four new combinations are proposed: Enneastigmafulva (Malloch, 1934), Enneastigmahenanensis (Ge & Fan, 1982), Enneastigmalengshanensis (Xue, 2001) and Hylemyaqinghaiensis (Fan, Chen & Ma, 1989). Eremomyiaturbida Huckett, 1951 is revived from synonymy with Chortophilatriticiperda Stein, 1900 (current name Eutrichotaturbida). One subspecies is upgraded to species: Adiaasiatica Fan, 1988. The following eight new synonymies are proposed: Deliapectinatorfuscilateralis Fan in Fan & Zheng, 1992 with Deliapectinator Suwa, 1984; Eremomyiapilimanapilimarginata Fan & Qian in Fan, Chen, Ma & Ge, 1982 with Eremomyiaturbida Huckett, 1951 (current name Eutrichotaturbida); Lopesohylemya Fan, Chen & Ma, 1989 with Hylemya Robineau-Desvoidy, 1830; Deliomyia Fan in Fan et al., 1988 with Subhylemyia Ringdahl, 1933; Hydrophoriadisticrassa Xue & Bai, 2009 with Hydrophoriapullata Wu, Liu & Wei, 1995 (current name Zaphnepullata); Heteroterma Wei, 2006 with Scathophaga Meigen, 1803; Heterotermafanjingensis Wei, 2006 with Scathophagacurtipilata Feng, 2002; Scatomyzafansipanicola Ozerov in Ozerov & Krivosheina, 2011 with Scathophagacurtipilata Feng, 2002. The genus Heteroterma Wei, 2006 and species Heterotermafanjingensis Wei, 2006 are reassigned from Anthomyiidae to Scathophagidae.

It is shown that a total of eight pre-existing genus-group names in Diptera were "borrowed" and deliberately given new identities in the systematic works of J.C. Fabricius: Bibio Fabricius, 1775, Ceria Fabricius, 1794, Hirtea Fabricius, 1798, Mulio Fabricius, 1798, Scatophaga Fabricius, 1805, Sicus Fabricius, 1798, Thereva Fabricius, 1798 and Voluccella Fabricius, 1794. These names are reviewed from the standpoint that they are nomenclaturally available as intentional homonymous proposals of names for new genus-group taxa. New type-species designations are made for Bibio Fabricius, Mulio Fabricius, and Scatophaga Fabricius. Bibio Fabricius, 1775 is recognized as a senior synonym of Thereva Latreille, 1797, syn. n., but is invalid as it is a junior homonym of Bibio Geoffroy, 1762. Scatophaga Fabricius, 1805 is recognized as a junior synonym of Psila Meigen, 1803, syn. n. The nominal species Musca suilla Fabricius, 1794 has been misinterpreted as a species of Scathophaga Meigen, 1803 by subsequent authors. Scathophaga spurca Meigen, 1826 is revived as the valid name for Scathophaga suilla auct. nec (Fabricius, 1794), stat. rev. A lectotype is designated for Musca suilla Fabricius and it is shown to belong to the scathophagid Norellisoma spinimanum (Fallén, 1819), syn. n. In order to maintain stability of nomenclature and prevailing usage, reversal of precedence is invoked to declare Cordylura spinimana Fallén, 1819 as a nomen protectum and Musca suilla Fabricius, 1794 as a nomen oblitum.

An updated checklist of the the genera and species of Anthomyiidae (Diptera) found in Finland is provided.

Fauna Europaea is Europe's main zoological taxonomic index, making the scientific names and distributions of all living, currently known, multicellular, European land and freshwater animals species integrally available in one authoritative database. Fauna Europaea covers about 260,000 taxon names, including 145,000 accepted (sub)species, assembled by a large network of (>400) leading specialists, using advanced electronic tools for data collations with data quality assured through sophisticated validation routines. Fauna Europaea started in 2000 as an EC funded FP5 project and provides a unique taxonomic reference for many user-groups such as scientists, governments, industries, nature conservation communities and educational programs. Fauna Europaea was formally accepted as an INSPIRE standard for Europe, as part of the European Taxonomic Backbone established in PESI. Fauna Europaea provides a public web portal at faunaeur.org with links to other key biodiversity services, is installed as a taxonomic backbone in wide range of biodiversity services and actively contributes to biodiversity informatics innovations in various initiatives and EC programs.

New synonymies in the genus Spilogona Schnabl, 1911 are proposed: S. novaesibiriae (Frey, 1915) = S. obsoleta (Malloch, 1920), syn. nov.; S. trianguligera (Zetterstedt, 1838) = S. setinervis (Huckett, 1932), syn. nov. Spilogona trianguligera and S. tendipes (Malloch, 1920) are newly recorded from Greenland, and S. trianguligera also from W Siberia. The female of S. vikhrevi Sorokina, 2010 is described and the species in newly recorded from Wrangel Island (Far East Russia).

The four nominal species currently included in the anthomyiid genus Chirosiomima Hennig, 1966 are critically assessed and redescribed. It is shown that the type species of Chirosiomima was originally misidentified. Chirosiomima obscurinervis (Emden, 1941) is resurrected from synonymy of C. gestroi (Séguy, 1930). Chirosiomima collini Ackland, 1968 is transferred to Botanophila Lioy (comb. nov.) and C. curtigena (Ringdahl, 1935) to Ringdahlia gen. nov. (comb. nov.). The previously unknown male of C. gestroi and female of R. curtigena (Ringdahl) are described.

The number of described species on the planet is about 1.9 million, with ca. 17,000 new species described annually, mostly from the tropics. However, taxonomy is usually described as a science in crisis, lacking manpower and funding, a politically acknowledged problem known as the Taxonomic Impediment. Using data from the Fauna Europaea database and the Zoological Record, we show that contrary to general belief, developed and heavily-studied parts of the world are important reservoirs of unknown species. In Europe, new species of multicellular terrestrial and freshwater animals are being discovered and named at an unprecedented rate: since the 1950s, more than 770 new species are on average described each year from Europe, which add to the 125,000 terrestrial and freshwater multicellular species already known in this region. There is no sign of having reached a plateau that would allow for the assessment of the magnitude of European biodiversity. More remarkably, over 60% of these new species are described by non-professional taxonomists. Amateurs are recognized as an essential part of the workforce in ecology and astronomy, but the magnitude of non-professional taxonomist contributions to alpha-taxonomy has not been fully realized until now. Our results stress the importance of developing a system that better supports and guides this formidable workforce, as we seek to overcome the Taxonomic Impediment and speed up the process of describing the planetary biodiversity before it is too late.

The natural occurrence and host range of species of the insect pathogenic fungal genus Strongwellsea [Zygomycota: Entomophthorales] were studied by extensive sampling and examination of adult Diptera [Cyclorrhapha]. The host range for Strongwellsea spp. was significantly enlarged. Three families were documented as new hosts: Muscidae (three species), Calliphoridae (one species), and Sarcophagidae (one species). Further, within the family Anthomyiidae six new host species were recorded and three new host species were documented in the Fanniidae. Strongwellsea castrans was identified as the pathogen in the Anthomyiids, while records from Fanniidae belonged to S. magna. The records of S. magna were the first outside the type locality (California). Primary conidia morphology indicated that muscid and calliphorid species were infected by three undescribed species of Strongwellsea. For the sarcophagid fly, no conidia were encountered, so the Strongwellsea species could not be identified. The tested sampling methods had each different advantages. Sweep netting and diagnosis in situ gave the best opportunity to sample a high number of infected dipterans per time unit spend, while sweep netting followed by incubation in the laboratory was the only method for the documentation of resting spores. The prevalence of S. castrans in the cabbage root fly Delia radicum was obtained by two methods: Samples collected by sweep net and incubated and water trap samples. Water trap captures gave higher prevalences of conidial infections than sweep-net captures. Measured prevalences of Strongwellsea spp. infections are therefore highly dependent on sampling method. The occurrence of resting spores of S. castrans in D. radicum was almost exclusively restricted to females and varied during the season. In samples from 1988 through 1993, no infected females in June contained resting spores, while 43.0% of the S. castrans-infected females from samples in August contained resting spores. During September and October, a decreasing proportion of S. castrans-infected D. radicum contained resting spores. The results document that species from the genus Strongwellsea are common fungal pathogens of adult flies from different families, occasionally with high prevalences. It also appears that the two described species of Strongwellsea, S. castrans and S. magna, have a range of dipterous host species that may always belong to a single family, Anthomyiidae and Fanniidae, respectively. Our data shows also that the host family Muscidae may be exploited by two new species of Strongwellsea. Copyright 1999 Academic Press.