Abstract

Flies of the monogeneric Australasian family Fergusoninidae (Diptera) and nematodes of the genus Fergusobia Currie (Tylenchida : Neotylenchidae) together form galls on various Myrtaceae, in the only recorded mutualism between flies and nematodes. New species of Fergusonina Malloch gall-forming flies are here described from the broad-leaved Melaleuca leucadendra species-complex (Myrtaceae), which includes M. quinquenervia (Cav.) S. T. Blake, an invasive weed outside its natural range. The putatively monophyletic Fergusonina turneri species-group is defined to accommodate: F. turneri, sp. nov.; F. burrowsi, sp. nov.; F. centeri, sp. nov.; F. goolsbyi, sp. nov.; F. makinsoni, sp. nov.; F. purcelli, sp. nov.; and F. schefferae, sp. nov. Partial descriptions are provided for further unnamed species from the M. leucadendra species-complex, and for an additional unassigned species from a narrow-leaved Melaleuca. The fly–nematode associations are species-specific and appear to have a high degree of host specificity within the Myrtaceae. Information on the mutualist nematodes and host plant associations are presented, together with two keys to species of Fergusonina: one based on adult characters, and one (for field workers) based on larva, puparium and gall characters and host and nematode associations.