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Many control methods target agricultural pests’ reproductive traits and so, knowledge of these traits is crucial. The seedcorn maggot, Delia platura (Diptera: Anthomyiidae), is reported as a cosmopolitan polyphagous pest species which can be found in high numbers in numerous crops. Two morphologically identical genetic lines of D. platura (H- and N- lines) with distinct distribution ranges were recently discovered. While many biological traits have been described for D. platura, no study to date has been conducted on the life history strategies and reproductive behaviors of its two lines. Using laboratory-reared colonies originating from the Montérégie region in Québec, this project investigates the effect of group composition (sex-ratio and density) on the mating success and pre-oviposition period of the two D. platura lines. We found a substantial increase in mating success with increasing proportion of males within mating groups for both lines while group density had negligeable effects. These results corroborate reports of D. platura high-density swarms in which sex ratios are usually male-biased. The pre-oviposition period decreased as the ratio of males to female increased at low density only for the N-line while the opposite trend was observed at high density for both lines. These results suggest differences between the mating systems of these two lines, with the H-line females being choosier towards potential mates than those of the N-line. We also describe reproductive traits of both lines along with their implications for integrated pest management strategies such as the sterile insect technique or the release of individuals carrying pathogens, both of which must take into account the high degree of sexual selection present in such group contexts. Keywords: reproductive biology, mating dynamics, seedcorn maggot, swarms

The Canadian Diptera fauna is updated. Numbers of species currently known from Canada, total Barcode Index Numbers (BINs), and estimated numbers of undescribed or unrecorded species are provided for each family. An overview of recent changes in the systematics and Canadian faunistics of major groups is provided as well as some general information on biology and life history. A total of 116 families and 9620 described species of Canadian Diptera are reported, representing more than a 36% increase in species numbers since the last comparable assessment by JF McAlpine et al. (1979). Almost 30,000 BINs have so far been obtained from flies in Canada. Estimates of additional number of species remaining to be documented in the country range from 5200 to 20,400.

The North American fauna of Drymeia Meigen was studied. Four new species are described (Drymeia huckettisp. nov., Drymeia pontisp. nov., Drymeia vockerothisp. nov., Drymeia woodorumsp. nov.), and three new synonymies are proposed: Drymeia amnicola (Huckett, 1966) (= Drymeia rivalis (Huckett, 1966), syn. nov.); Drymeia glacialis (Rondani, 1866) (= Drymeia alpicola (Rondani, 1871), syn. nov.); and Drymeia spinitarsis (Aldrich, 1918) (= Drymeia longiseta Sorokina & Pont, 2015, syn. nov.). An annotated checklist, DNA barcodes (when available), and keys for each sex of the 24 named species of North American Drymeia are provided. The utility of DNA barcodes for the identification of Drymeia species across a wide geographical range was explored using sequences from five countries. A match between morphology and DNA barcodes was found for 71% (22/31) of species studied (including three unnamed taxa). The remaining nine species clustered into two groups of taxa with very little interspecific variation within clusters (groups of two and seven species). Caution is advised against using DNA barcoding as the only determination tool for Drymeia material without prior knowledge of its limitations for certain species groups.

Soil pests of cruciferous crops in Mexico have been gaining importance in recent years; such is the case of Delia spp. (Robineau-Desvoidy) (Diptera, Anthomyiidae), of which, to date, there are no studies on the correct identification of associated species, as well as the range of hosts. In an integrated pest management program, it is essential to know this information to design and implement adequate phytosanitary measures. Plants infested by Delia spp. were collected in the states of Guanajuato, Puebla, and Mexico from June to November 2017 and March to December 2018 in commercial plantations of cruciferous crops (Brassica oleracea L. var. italica, botrytis and capitata), B. napus L., and Raphanus sativus L.) as well as some cruciferous weeds (R. raphanistrum L., Sisymbrium irio L., B. campestris L., Capsella bursa-pastoris L., and Lepidium virginicum L.) in the edges of these crops. The two species found in this study, Delia planipalpis (Stein) and Delia platura (Meigen), identified using male genitalia was corroborated by molecular techniques. Both species emerged from all the sampled hosts, except for C. bursa-pastoris and L. virginicum. The association of the two species in cruciferous crops and weeds, provides valuable information for the management of these insects not only in cruciferous crops but other ones that are strongly attacked by D. platura.

The seedcorn maggot Delia platura (Meigen), and the bean seed maggot Delia florilega (Zetterstedt) can cause considerable feeding damage to a wide range of cultivated crops. The recent discovery of two distinct genetic lines of D. platura, each with a unique distribution pattern overlapping only in eastern Canada, suggests the presence of a new cryptic species for the group. The reliable identification of the three species/lines in the seedcorn maggot complex is crucial to our understanding of their distribution, phenology, and respective contribution to crop damage as well as to the development of specific integrated pest management approaches. As these taxa are morphologically indistinguishable in the immature stages, we developed a high-resolution melting PCR (HRM) assay using primers amplifying a variable 96-bp PCR product in the CO1 mitochondrial gene for rapid and economical identification of specimens. The three species/lines exhibited distinguishable melting profiles based on their different Tm values (between 0.4 and 0.9°C) and identification results based on HRM and DNA sequencing were congruent for all specimens in the validation data set (n = 100). We then used the new, highly sensitive HRM assay to identify survey specimens from the seedcorn maggot complex collected in Quebec, Canada, between 2017 and 2019. Progress curves developed to document the temporal occurrence patterns of each species/lines indicate differences between taxa, with the N-line (BOLD:AAA3453) of D. platura appearing approximately 17 d before D. florilega (BOLD:ACR4394) and the H-line (BOLD:AAG2511) of D. platura.

Soil pests of cruciferous crops in Mexico have been gaining importance in recent years; such is the case of Delia spp. (Robineau-Desvoidy) (Diptera, Anthomyiidae), of which, to date, there are no studies on the correct identification of associated species, as well as the range of hosts. In an integrated pest management program, it is essential to know this information to design and implement adequate phytosanitary measures. Plants infested by Delia spp. were collected in the states of Guanajuato, Puebla, and Mexico from June to November 2017 and March to December 2018 in commercial plantations of cruciferous crops (Brassica oleracea L. var. italica, botrytis and capitata), B. napus L., and Raphanus sativus L.) as well as some cruciferous weeds (R. raphanistrum L., Sisymbrium irio L., B. campestris L., Capsella bursa-pastoris L., and Lepidium virginicum L.) in the edges of these crops. The two species found in this study, Delia planipalpis (Stein) and Delia platura (Meigen), identified using male genitalia was corroborated by molecular techniques. Both species emerged from all the sampled hosts, except for C. bursa-pastoris and L. virginicum. The association of the two species in cruciferous crops and weeds, provides valuable information for the management of these insects not only in cruciferous crops but other ones that are strongly attacked by D. platura.

Over the last decades, aerial insectivorous birds have been declining in both North America and Europe. Those declines have been hypothetically attributed to a decrease in prey availability caused by agricultural intensification, but empirical evidence remains scarce. Here, we quantify the effect of landscape composition on the abundance and diversity of potential prey of Tree Swallows (Tachycineta bicolor (Vieillot, 1808)) and on nestling diet in southern Quebec, Canada. We collected food boluses from nestlings and compared their composition with spatiotemporally corresponding samples from traps on farms distributed along a gradient of agricultural intensification. The diet of nestlings was mostly composed of Diptera, both in biomass and abundance, but by mid-June, these decreased with increasing proportions of intensively cultivated crops within 500 m of the nests. Trap catches for Diptera and all arthropods combined followed the same trends. Yet, the associations between Diptera subgroups (Nematocera, non-schizophoran Brachycera, Schizophora (Calyptratae), and Schizophora (Acalyptratae)) and landscape composition differed between traps and boluses, suggesting that prey selection was altered by agricultural intensification. Our results suggest that agriculture can alter the availability of preferred prey for aerial insectivores, and further studies should evaluate the impact of prey availability to explain the decline of aerial insectivores.

Understanding the interactions between parasites, hosts, and their shared environment is central to ecology. Variation in infestation prevalence may be the result of varying environmental and population characteristics; however, variations in parasitism may also depend on individual characteristics that influence both the exposure and susceptibility to parasites. Using 12 years of data from a population of wild eastern chipmunks relying on pulsed food resources, we investigated the determinants of bot fly parasitism at both the population and individual level. We assessed the relationship between infestation prevalence and weather conditions, population size and food abundance. Then, we assessed the relationship between infestation intensity and chipmunk behavior, sex, age, body mass and food abundance. Precipitation, temperature and population size were positively related to infestation prevalence, while beech masts were negatively related to infestation prevalence, highlighting the importance of local environmental conditions on hosts and parasites. We also found that the influence of activity and exploration on infestation intensity varied according to sex in adults. More active and faster exploring males had more parasites compared to females, suggesting that reproductive behaviors may influence parasite exposure. For juveniles, infestation intensity was greater when juveniles emerged in the spring as opposed to fall, possibly because spring emergence is synchronized with the peak of bot fly eggs in the environment, low food availability and longer activity period. Our results suggest that the environmental, population and host characteristics that are advantageous for reproduction and resource acquisition may come at the cost of increasing parasitism.

SUMMARYWidespread access to the internet is offering new possibilities for data collection in surveillance. We explore, in this study, the possibility of using an electronic tool to monitor occurrence of the tick vector of Lyme disease, Ixodes scapularis. The study aimed to compare the capacity for ticks to be identified in web-based submissions of digital images/photographs, to the traditional specimen-based identification method used by the provincial public health laboratory in Quebec, Canada. Forty-one veterinary clinics participated in the study by submitting digital images of ticks collected from pets via a website for image-based identification by an entomologist. The tick specimens were then sent to the provincial public health laboratory to be identified by the ‘gold standard’ method using a microscope. Of the images submitted online, 74·3% (284/382) were considered of high-enough quality to allow identification. The laboratory identified 382 tick specimens from seven different species, with I. scapularis representing 76% of the total submissions. Of the 284 ticks suitable for image-based species identification, 276 (97·2%) were correctly identified (Kappa statistic of 0·92, Z = 15·46, P < 0·001). This study demonstrates that image-based tick identification may be an accurate and useful method of detecting ticks for surveillance when images are of suitable quality.

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.

Made available in DSpace on 2019-10-06T15:56:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-12-01 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. Entomology Section Natural History Museum of Los Angeles County, 900 Exposition Boulevard Royal British Columbia Museum and the American Museum of Natural History, 691-8th Ave. SE Department of Plant and Environmental Sciences Poole Agricultural Center Clemson University, 130 McGinty Court, E-143 Depto. de Biologia FFCLRP Universidade de São Paulo, Av. Bandeirantes 3900 Great Lakes Forestry Centre Canadian Forest Service Natural Resources Canada, 1219 Queen St. E. Australian Museum, 1 William Street Department of Natural Resource Sciences McGill University Macdonald Campus Canadian National Collection of Insects Invertebrate Biodiversity Agriculture and Agri-Food Canada, K.W. Neatby Building, 960 Carling Avenue Department of Biological Sciences Spaulding Hall University of New Hampshire Department of Biological Sciences Wright State University, 3640 Colonel Glenn Hwy Instituto Federal do Triângulo Mineiro – Campus Uberaba. Rua João Batista Ribeiro 4000 Distrito Industrial II Departamento de Zoologia Universidade Federal do Paraná Jardim das Américas Mississippi Entomological Museum Mississippi State University, 100 Old Highway 12, P.O. Drawer 9775 Department of Biology Western Kentucky University Integrative Research Center Field Museum of Natural History Independent Investigator California State Collection of Arthropods, 2683 Tam O’ Shanter Dr., El Dorado Hills California Department of Food and Agriculture California State Collection of Arthropods, 3294 Meadowview Rd. The Academy of Natural Sciences of Drexel University, 1900 Ben Franklin Parkway American Museum of Natural History, Central Park West at 79th St. Department of Entomology University of California Riverside, 900 University Ave. Zoological Museum Biodiversity Unit FI-20014 University of Turku Instituto de Ecología A.C. (INECOL) Red Ambiente y Sustentabilidad, Carretera Antigua a Coatepec 351, Col El Haya, Xalapa Station Linné, Ölands Skogsby 161 I. I. Schmalhausen Institute of Zoology of the National Academy of Sciences of Ukraine, Bogdan Chmielnicki St. 15 Universidad de Panama Department of Natural History University Museum of Bergen University of Bergen, P.O. Box 7800 Agriculture and Agri-Food Canada, 960 Carling Avenue School of Environmental Sciences University of Guelph Department of Entomology Smithsonian Institution, PO Box 37012, MRC 169 Natural History Museum of Denmark, Universitetsparken 15 Institute of Evolutionary Biology and Environmental Studies University of Zurich, Winterthurerstrasse 190 Systematic Entomology Laboratory USDA ARS c/o National Museum of Natural History, MRC-168, P.O. Box 37012 Departamento de Sistemática e Ecologia CCEN Universidade Federal da Paraíba, Castelo Branco, s/n Research Institute for Nature and Forest (INBO), Kliniekstraat 25 Research Group Terrestrial Ecology (TEREC) Ghent University, K.L.Ledeganckstraat 35 Entomology Unit Royal Belgian Institute for Natural Sciences (RBINS), Vautierstraat 29 USDA Forest Service Rocky Mountain Research Station Forestry Sciences Laboratory, 1648 S. 7th Avenue Department of Biological Sciences Bishop’s University, 2600 College Street UNESP - Univ Estadual Paulista Faculdade de Ciências Agrárias e Veterinárias Departamento de Morfologia e Fisiologia Animal; Via de Acesso Prof. Paulo Donato Castellane s/n Canadian National Collection of Insects & Canadian Food Inspection Agency OPL-Entomology, K.W. Neatby Bldg., C.E.F., 960 Carling Ave. Department of Biological Sciences University of Calgary, 2500 University Drive NW Finnish Museum of Natural History Zoology Unit University of Helsinki Washington State University, 2533 Inter Avenue Bohart Museum of Entomology University of California, One Shields Avenue Instituto Nacional de Biodiversidad (INBio) UNESP - Univ Estadual Paulista Faculdade de Ciências Agrárias e Veterinárias Departamento de Morfologia e Fisiologia Animal; Via de Acesso Prof. Paulo Donato Castellane s/n

Insects are particularly vulnerable to rapid environmental changes, which are disproportionally affecting high latitudes. Increased temperature could influence insect species differentially and reshape assemblages over time. We quantified temporal assemblage turnover of Arctic Diptera (flies) in the Muscidae, one of the most diverse and abundant families of Arctic insects, using time series data from Zackenberg, North-East Greenland. We measured temporal patterns of abundance, diversity, and composition of muscid assemblages in wet fen, mesic and arid heath habitats from yearly collections spanning 1996–2014 and tested their relationship to climate. A total of 18,385 individuals representing 16 species of muscid flies were identified. A significant decrease of 80% of total muscid abundance was observed during the study period. Species richness declined in each habitat type but this trend was not significant across habitats. The number of common and abundant species also decreased significantly over time across habitats revealing a temporal modification of species evenness. Significant temporal changes in composition observed in the wet fen and across habitats were mainly driven by a change in relative abundance of certain species rather than by species replacement. Shift in composition in each habitat and decline in muscid abundance across habitats were associated with summer temperature, which has significantly increased over the study period. However, relationships between temperature and muscid abundance at the species level were noticeable for a few species only. Significant directional change in composition was documented in the wet fen but no biotic homogenization across habitats was observed. As one of the few studies of species-level changes in abundance, diversity and composition of an insect taxon in the Arctic over the past two decades, our study shows that habitat types may modulate insect species responses to recent climate change and that contrasting species responses can alter species assemblages within a few decades. This article is protected by copyright. All rights reserved.

We described the community composition of the ectoparasitic flies Protocalliphora Hough (Diptera: Calliphoridae) and their Nasonia (Ashmead) (Hymenoptera: Pteromalidae) parasitoids collected from tree swallow, Tachycineta bicolor (Vieillot), nests in southern Québec, Canada, in 2008 and 2009. The prevalence of nest infestation by Protocalliphora was 70.8% in 2008 and 34.6% in 2009. The average parasitic burden of Protocalliphora spp. was estimated at 5.53 (±5.61 SD) pupae per nestling for 2008 and 4.66 (±9.31 SD) pupae per nestling for 2009. The percentage of nests containing Protocalliphora pupae parasitized by Nasonia spp. was of 85.3% in 2008 and 67.2% in 2009. Three species of Protocalliphora were collected—Protocalliphora sialia Shannon & Dobroscky, Protocalliphora bennetti Whitworth, and Protocalliphora metallica (Townsend)—and two species of Nasonia, Nasonia vitripennis (Walker) and Nasonia giraulti Darling. This is the first record of P. bennetti and N. giraulti in the province of Québec. Our findings provide further evidence for observation made previously that altricial bird nests are more frequently and more heavily infested by blow flies in western than in eastern North America. Our data also suggest that more than a quarter of the tree swallow within the study area are exposed to high levels of ectoparasitism that could negatively affect their health.

A survey of muscid flies from Churchill, Manitoba, Canada, in 2007 yielded 155 species. Some components of species richness and composition of this contemporary assemblage were compared with those of a historical (pre-1965) assemblage, and the contribution of the three collecting methods used in the 2007 survey protocol was evaluated. Estimates of species richness indicated that Malaise traps yielded more species than did pan traps or sweep netting, and that species composition did not differ significantly between Malaise trap and pan trap catches. These results suggest that Malaise traps and sweep netting are adequate methods to survey northern Muscidae. We report little difference in estimated species richness and composition between time periods for material collected by sweep netting. When all material from the 2007 survey was pooled, 87% of the pre-1965 species were collected again in 2007. Most nonoverlapping species between time periods were rare in samples and (or) collected by different methods, suggesting a failure to detect as the most likely explanation for their absence in one assemblage. Nevertheless, the proportion of aquatic and semiaquatic species of Spilogona Schnabl was more than twice as high in the list of species not recovered in 2007 than in the pre-1965 assemblage.

The muscid genus Thricops Rondani comprises forty-four species and two subspecies restricted to the northern hemisphere. A species-level phylogenetic analysis of Thricops was conducted using forty-four morphological characters, 426 bp of the nuclear gene white and 523 bp spanning the 5′ end of the cytochrome c oxidase subunit I (COI), the tRNA leucine gene (L2 region) and the 3′ end of the cytochrome c oxidase subunit II (COII). Thirty-nine species and two subspecies of Thricops were included in the analysis. Two species of Azelia Robineau-Desvoidy and one species of Hydrotaea Robineau-Desvoidy were used as outgroups. Morphological characters were coded for all included species, the mitochondrial gene fragment (COI + II) was sequenced for a subset of seventeen species of Thricops and three outgroup species, and white for twelve of those seventeen Thricops species and two outgroup species. Six separate maximum parsimony analyses were performed on three taxon sets of different sizes (n = 14, n = 20, n = 44). Results from the partition homogeneity test indicated no significant incongruence between data partitions, and four combined maximum parsimony analyses were conducted (DNA + morphology for n = 14; COI + II + morphology for n = 20; DNA + morphology for n = 20; DNA + morphology for n = 44). The relative contribution of each data partition to individual nodes was assessed using partitioned Bremer support. Strict consensus trees resulting from the unweighted analyses of each dataset are presented. Combination of datasets increased resolution for the small taxon set (n = 14), but not for the larger ones (n = 20, n = 44), most probably due to increasing amounts of missing data in the larger taxon sets. Results from both individual and combined analyses of the smaller taxon sets (n = 14, n = 20) provided support for the monophyly of Thricops and a complete division of the genus into two monophyletic subgroups. The strict consensus cladograms resulting from the analysis of the morphological data alone and the combined data for the large taxa set (n = 44) both supported the monophyly of the genus, but placed the species Thricops foveolatus (Zetterstedt) and Thricops bukowskii (Ringdahl) at the base of the ingroup, in a polytomy with a relatively well-resolved branch comprising all remaining species of the genus. The basal position of these two species, included in the morphological taxon set but absent in the others, illustrates the potential pitfalls of taxon sampling and missing data in phylogenetic analyses. The synonymy of Alloeostylus with Thricops as proposed by previous authors was supported by our results. Relative contributions of different data partitions is discussed, with the mitochondrial sequence generally providing finer resolution and better branch support than white.

The Holarctic genus Cetema Hendel is revised, with special reference to the Nearctic fauna. There are four Nearctic species: C. elongata Meigen; C. nigripalpis sp. n., C. procera Loew, and C. subvittata Loew. This is the first record of the Palaearctic species C. elongata in the Nearctic region. All Nearctic species are described and illustrated. The Palaearctic species C. paramyopina Collin is synonymized with C. neglecta Tonnoir and a key to all described species of Cetema is provided. A phylogenetic analysis supports the monophyly of the genus, as well as the monophyly of the subgenera Archecetema Nartshuk and Cetema. The Nearctic species do not form a monophyletic group. Zoogeographic analysis suggests that the genus originated in the eastern Palaearctic and subsequently colonized North America via a Beringian connection, probably in the early to mid-Tertiary. Following speciation in the eastern Nearctic, the more derived lineages of Cetema recolonized the western Palaearctic, probably via a North Atlantic land connection prior to the late Miocene.

Background Various methods have been proposed to assign unknown specimens to known species using their DNA barcodes, while others have focused on using genetic divergence thresholds to estimate “species” diversity for a taxon, without a well-developed taxonomy and/or an extensive reference library of DNA barcodes. The major goals of the present work were to: a) conduct the largest species-level barcoding study of the Muscidae to date and characterize the range of genetic divergence values in the northern Nearctic fauna; b) evaluate the correspondence between morphospecies and barcode groupings defined using both clustering-based and threshold-based approaches; and c) use the reference library produced to address taxonomic issues. Results Our data set included 1114 individuals and their COI sequences (951 from Churchill, Manitoba), representing 160 morphologically-determined species from 25 genera, covering 89% of the known fauna of Churchill and 23% of the Nearctic fauna. Following an iterative process through which all specimens belonging to taxa with anomalous divergence values and/or monophyly issues were re-examined, identity was modified for 9 taxa, including the reinstatement of Phaonia luteva (Walker) stat. nov. as a species distinct from Phaonia errans (Meigen). In the post-reassessment data set, no distinct gap was found between maximum pairwise intraspecific distances (range 0.00-3.01%) and minimum interspecific distances (range: 0.77-11.33%). Nevertheless, using a clustering-based approach, all individuals within 98% of species grouped with their conspecifics with high (>95%) bootstrap support; in contrast, a maximum species discrimination rate of 90% was obtained at the optimal threshold of 1.2%. DNA barcoding enabled the determination of females from 5 ambiguous species pairs and confirmed that 16 morphospecies were genetically distinct from named taxa. There were morphological differences among all distinct genetic clusters; thus, no cases of cryptic species were detected. Conclusions Our findings reveal the great utility of building a well-populated, species-level reference barcode database against which to compare unknowns. When such a library is unavailable, it is still possible to obtain a fairly accurate (within ~10%) rapid assessment of species richness based upon a barcode divergence threshold alone, but this approach is most accurate when the threshold is tuned to a particular taxon.

The large striking flies of the genus Mesembrina are typically found in boreal forest and at high elevations throughout the Northern Hemisphere. While it is known that most species are decomposers of ungulate dung, biological and taxonomic information on the New World fauna of Mesembrina is mostly out of date or unreliable. Consequently, the Nearctic taxa have been revised, resulting in the new synonymy of Mesembrina solitaria (Knab) with Mesembrina decipiens Loew, making M. decipiens the only species of the genus with a confirmed Holarctic distribution. Mesembrina latreillii Robineau-Desvoidy, contrary to previous indications, may be restricted to the Nearctic Region. The first Neotropical member of the genus, Mesembrina nigribasis sp. nov. is described. To place the New World fauna in context, a key to the world species of Mesembrina is provided. This key includes a species designated by Hennig as “resplendens subspecies” from the Palaearctic, which is a distinct but undescribed species.

Although several studies have examined the influence of landscape structure and agricultural intensification on species abundance and diversity, few have addressed how these impact populations across multiple trophic levels. We investigated the effects of landscape structure on the tri-trophic interactions between a bird host (the Tree Swallow Tachycineta bicolor (Vieillot)), its blowfly ectoparasites (Protocalliphora Hough), and their parasitoid wasps (Nasonia Ashmead) across 13 spatial scales, along a gradient of agricultural intensification covering 10,200 km 2 in southern Quebec, Canada. We showed that the three taxa responded to landscape structure at distinctive spatial scales that are relative to their size rather than their trophic rank. This response, however, differed according to habitat type. The three organisms responded to the amount of intensive cultures (maize, soybean and other cereals) at smaller spatial scales than to the amount of extensive cultures (hayfields and pastures). Although the number of Tree Swallow fledglings, the number of Protocalliphora sialia Shannon & Dobroscky pupae and the number of P. sialia pupae parasitized by Nasonia sp. per nest were negatively affected by agricultural intensification, our data do not support the prediction that organisms at the higher trophic levels are more susceptible to habitat degradation. Here, ectoparasites at the second trophic level were disproportionally affected by agricultural intensification; the abundance of P. sialia decreased by 80% along the gradient of agricultural intensification compared to a 20% and 35% reduction in the number of Tree Swallow fledglings and in the level of parasitism by Nasonia sp., respectively. Our work highlights the importance of designing protocols that take spatial aspects of trophic interactions into account when studying the impact of habitat loss and fragmentation on populations and communities, as these interactions dictate local biodiversity and community function. Furthermore, our results highlight the importance of considering multiple landscape parameters when identifying the functional spatial scales of an organism, as a failure to do so could lead to an underestimation of the area it uses.