Hitchhiking across continents: phoresy of pseudoscorpions (Arachnida, Pseudoscorpiones) on Diptera, with new European records

Phoresy is an important dispersal strategy in pseudoscorpions, yet associations with Diptera have not been comprehensively revised for more than two decades. An updated synthesis of pseudoscorpion-Diptera phoresy is presented based on newly collected European material, a revision of previously studied Slovak material, a critical reassessment of worldwide published records, and available fossil evidence. In total, 11 previously unreported cases of pseudoscorpion phoresy from four European countries are documented, including the first records of Dactylochelifer degeerii (C.L. Koch, 1835) from France and of Pselaphochernes scorpioides (Hermann, 1804) from Slovenia. Seven dipteran species and three dipteran families are newly recorded worldwide as hosts of pseudoscorpion phoresy, and one case of multiple phoresy was recorded from Slovakia. Altogether, 172 records spanning the period from 1761 to 2025 were compiled and evaluated. Compared with previous syntheses, the number of known dipteran hosts was increased to 74 species from 30 families, and pseudoscorpion phoronts to 39 species from seven families. This study provides the most comprehensive overview of pseudoscorpion-Diptera phoresy to date and establishes a robust framework for future taxonomic, ecological, and evolutionary studies.