Fergusobia; ASSOCIATIONS-; Fergusonina flavicornis (Diptera); Relationships in plant galls; PLANT-HOSTS; Eucalyptus camaldulensis; Gall biology, relationships with Diptera; SOUTH-AUSTRALIA; Goolwa; Relationships with Diptera in plant galls Fergusonina flavicornis; ASSOCIATIONS-; Fergusobia (Nematoda) & Hymenoptera; Relationships & biology in plant galls; HYMENOPTERAN-PARASITES; Parasite survey including new species, plant galls; PLANT-HOSTS; Eucalyptus camaldulensis; Gall formation & associations with Hymenoptera & Nematoda; SOUTH-AUSTRALIA; Goolwa; Plant gall biology including relationships with Hymenoptera & Nematoda HYMENOPTERA-; ASSOCIATIONS-; Fergusonina flavicornis (Diptera); Relationships in plant galls including new species; DIPTERAN-HOSTS; Fergusonina flavicornis; Relationships in plant gall including new parasite species; SOUTH-AUSTRALIA; Goolwa; Associates & parasites of Diptera in plant galls including new species Galls initiated by the association of Fergusonina flavicornis Malloch (Insecta: Diptera: Fergusoninidae) and Fergusobia sp. (Nematoda: Sphaerulariidae) on Eucalyptus camaldulensis Dehnh. at Goolwa, South Australia were monitored during a single, late summer generation for emergence of flies and associated Hymenoptera. The morphology of the galls is described for the first time. A total of 12 hymenopteran species was reared from galls, twice the number previously recorded from Fergusonina/Fergusobia galls. There was a strong positive correlation between emergence of flies, combined totals of flies and wasps and gall size. Bracon fergusoninus sp. nov., a probable primary parasitoid of F. flavicornis larvae, is described. Notes on the biology and taxonomy of each hymenopteran species are presented along with an illustrated key to their identification.