This is the fourth `empidid' volume of the series `Fauna entomologica scandinavica', covering the Scandinavian species of what is undoubtedly the most difficult Palaearctic genus of the family Empididae, the genus Hilara Meigen, 1822. The format of the present volume is the same as in the preceding three volumes. The General part refers only briefly to the morphology of the adults, and is followed by sections on the Classification, Life history (covering feeding habits, epigamic behaviour, phenology), and a section on Zoogeography. All these sections are arranged as in the preceding empidid volumes, including the zoogeography section in which the Scandinavian species are classified into the usual six distributional groups.
The main part is the systematic treatment, which also follows the arrangement of the preceding empidid volumes. The `Key to Fennoscandian species' includes several additional species which do not receive a separate treatment in the following systematic part, but they are all given a clear diagnosis in the discussion of the most closely related Scandinavian species.
In all, 90 species of Hilara are treated in the present volume, of which 72 have been found to occur in Denmark and Fennoscandia. These further 18 species are included, as they may well occur within the area covered by this series although they have not yet been found there.