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.

Insect parasitoids may be an exception to the typical biogeographic pattern of increasing species richness at lower latitudes exhibited by most taxa. Evidence for this ‘anomalous’ latitudinal gradient has been derived from observations of hymenopteran parasitoids and it has been argued that other parasitoid groups should show a similar pattern of diversity. Several mechanisms have been proposed to explain this disparity, most notably the nasty host and resource fragmentation hypotheses. We review and evaluate these hypotheses with respect to tachinid flies (Diptera: Tachinidae), and bring to the argument evidence from eight trapping surveys from temperate and tropical regions in the Americas including the United States, Costa Rica, and Ecuador. We find no evidence that tachinid fly diversity is lower in the tropics than in the temperate region. Our results, along with other lines of evidence, rather suggest that New World Tachinidae likely conform to the same negative relationship between latitude and richness as their largely phytophagous host taxa. We discuss geographic patterns of tachinid diversity in relation to ecological and evolutionary processes, and why they may differ from their hymenopteran parasitoid counterparts. Parasitoid taxa appear to vary strongly in their diversity responses to latitude and we concur with previous researchers that more survey data are necessary to reach strong conclusions about parasitoid latitudinal diversity patterns.

The Eucelatoria ferox group is a lineage of 26 species of the New World genus Eucelatoria Townsend (Tachinidae) in which the female bears a distinctive sword-like piercer. The E. ferox group is revised and illustrated in detail, including nine species redescriptions and seventeen new species. This work also includes three new species synonyms and one new genus synonym. Three morphology-based subgroups are recognized and supported by genetic and host evidence as well as by geographic patterns. The E. ferox subgroup contains species with only two dorsal thoracic vittae on both the presutural and postsutural areas, including Eucelatoria ferox (Townsend), E. huitepecensis sp. nov., and E. inclani sp. nov. The E. gladiatrix subgroup contains those species with four dorsal thoracic vittae on both the presutural and postsutural areas, including Eucelatoria aurata (Townsend), E. auriceps (Aldrich), E. borealis sp. nov., E. charapensis (Townsend), E. crambivora sp. nov., E. falcata sp. nov., E. fordlandia sp. nov., E. gladiatrix (Townsend), E. jorgecortesi sp. nov., E. luctuosa (Wulp), E. rivalis (Reinhard), E. sabroskyi sp. nov., E. strigata (Wulp), E. texana (Reinhard), E. woodorum sp. nov., and E. yanayacu sp. nov. The E. kopis subgroup contains species with a single large dorsal thoracic vitta on the postsutural area and usually two vittae on the presutural area, including Eucelatoria gustavogutierrezi sp. nov., E. hafelei sp. nov., E. kopis sp. nov., E. makhaira sp. nov., E. ritavargasae sp. nov., E. sica sp. nov., and E. tenebrionis sp. nov. The following new synonymies are proposed: Proroglutea Townsend under Eucelatoria Townsend, syn. nov.; Eucelatoria fasciata (Townsend) and E. minima (Wulp) under E. strigata (Wulp), syn. nov.; Proroglutea pilligera Townsend under Eucelatoria gladiatrix (Townsend), syn. nov. Additionally, Telothyria lugens Wulp and Exorista obscurata Wulp are removed from synonymy with Eucelatoria luctuosa (Wulp) and resurrected as Eucelatoria lugens (Wulp) and E. obscurata (Wulp). The E. gladiatrix subgroup appears to be specialized on Crambidae (Lepidoptera) caterpillars, while the E. kopis subgroup parasitizes a variety of Lepidoptera families; host use for the E. ferox subgroup is unknown. The characteristic “leaf-rolling” habit of host families and visual evidence from rearing records suggests that the long piercers are used to penetrate leaf tissue for oviposition. Species of the E. ferox group are distributed throughout the Western Hemisphere from southern Canada to northern Argentina, with the highest species diversity and likely center of origin in the Central and South American tropics.