A taxonomic review of Palaearctic Peromyia Kieffer (Diptera: Cecidomyiidae, Micromyinae), with descriptions of thirty-eight new species mostly from Sweden

The taxonomy of Palaearctic Peromyia KIEFFER, 1894 is reviewed on the basis of specimens mostly from Sweden. Evidence from adult morphology and, if available, DNA barcode (COI) sequences are used for characterizing species. Of a total of 78 species, 38 are described as new: Peromyia acuminata spec. nov. (from Sweden, Germany, and Russia), P. angulosa spec. nov. (Norway, Sweden, Finland, Germany), P. angustior spec. nov. (Sweden), P. appositoides spec. nov. (Sweden), P. brandenburgensis spec. nov. (Germany), P. brutostylata spec. nov. (Sweden, Finland, Russia), P. clavata spec. nov. (Sweden, Germany), P. cognata spec. nov. (Norway, Sweden, Finland, Russia), P. consimilis spec. nov. (Norway, Sweden, Finland, Germany), P. constricta spec. nov. (Sweden, Finland, Germany), P. curvostylata spec. nov. (Sweden), P. despecta spec. nov. (Sweden, Finland, Russia, Germany), P. devia spec. nov. (Sweden, Germany), P. dupla spec. nov. (Sweden, Germany), P. gracilostylata spec. nov. (Norway, Sweden, Finland, Germany), P. grytsjoenensis spec. nov. (Sweden), P. hyalina spec. nov. (Sweden, Finland), P. inflata spec. nov. (Sweden, Finland, Germany, Japan), P. iuxtatruncata spec. nov. (Sweden, Finland, Russia, Germany), P. karstroemi spec. nov. (Sweden), P. lapponica spec. nov. (Sweden), P. lippertae spec. nov. (Sweden), P. lisatengoe spec. nov. (Sweden), P. longi- stylata spec. nov. (Norway, Sweden, Germany), P. manca spec. nov. (Norway, Sweden), P. monticorvina spec. nov. (Sweden), P. neglecta spec. nov. (Sweden, Finland, Germany), P. niederhofensis spec. nov. (Sweden, Germany), P. oelandica spec. nov. (Sweden), P. ombergensis spec. nov. (Sweden), P. pseudoborealis spec. nov. (Norway, Sweden, Japan), P. pumiloides spec. nov. (Norway, Sweden, Finland, Germany), P. quercinophila spec. nov. (Sweden), P. simulans spec. nov. (Sweden, Finland), P. stenshuvudensis spec. nov. (Sweden, Germany), P. trifidoides spec. nov. (Sweden), P. uleforsi spec. nov. (Sweden), and P. uniseriata spec. nov. (Sweden, Germany). The status as valid species is reinstated for P. brevispina YUKAWA, 1967 stat. restit. (released from synonymy with Joannisia fungicola KIEFFER, 1901), P. prominens YUKAWA, 1967 stat. restit. (released from synonymy with Campylomyza impexa SKUSE, 1888), P. subanatina MAMAEV {&} ZAITZEV, 1997 (released from synonymy with P. anatina MAMAEV {&} BEREST, 1990), and P. viklundi JASCHHOF, 1997 (released from synonymy with P. scutellata MAMAEV, 1990). The morphology of males is revised of P. anatina, P. angellifera JASCHHOF, 1997, P. apposita JASCHHOF, 1997, P. brevispina, P. caricis (KIEFFER, 1901), P. fungicola, P. prominens, P. ramosa (EDWARDS, 1938), P. neomexicana (FELT, 1913), P. scutellata, P. subanatina, P. subborealis JASCHHOF, 1997, P. truncata YUKAWA, 1967, and P. viklundi. COI sequences support the identity of 44 morphospecies and confirm that both P. impexa and P. photophila as presently defined are complexes of cryptic species. The threshold for separating species of Peromyia lies at 8 {%} genetic (K2P) distance. New faunistic records in Sweden are P. brevispina, P. maetoi JASCHHOF, 2001, P. neomexicana, P. revelata MAMAEV {&} BEREST, 1990, and P. viklundi. Peromyia pumila JASCHHOF, 2001 and P. truncata are deleted from the list of Swedish species. Recent advances in the study of Peromyia taxonomy and diversity are discussed in terms of methodology. Key