A re-assessment of the genera Holorusia Loew (=Ctenacroscelis Enderlein), Ischnotoma Skuse and Zelandotipula Alexander (Diptera: Tipulidae), with notes on their phylogeny and zoogeography

Summary

A short historical background to the genera considered is given. A review is made of a number of characters which had previously only been treated inconsistently, or not at all. As a result, the old-world genus Ctenacroscelis is merged with Holorusia sensu stricto, as represented by the isolated Californian type-species. All other species previously referred to Holorusia sensu lato are redistributed to two genera; the tropical South American and New Zealand forms are united into Zelandotipula; the Chilean element and the Australian species are united into Ischnotoma, the name Icriomastax Enderlein being resurrected as a subgenus to receive most of the Chilean species.

Tentative phylogenetic and zoogeographic observations are made. Holorusia and Ischnotoma are considered and discussed as sister-groups, whilst Zelandotipula is believed to be only distantly related. Zoogeographically Holorusia is seen as a successful Asiatic genus; Ischnotoma as a receding group, with extreme southern-continental distribution, having had a much wider distribution as indicated by the European Oligocene fossil Holorusia vasifera, transferred here to Ischnotoma. Zelandotipula is viewed as an essentially Neotropical genus, which has made one ‘invasion’ of New Zealand, probably in the geologically recent past.

Résumés of the principal features of the re-defined genera are given, together with systematic notes on certain species, and species catalogues giving distributions and all new name combinations.