The Mediterranean forest regions of Australia predominantly comprise native mallee scrub, eucalypt woodlands, exotic Pinus plantations, and commercial eucalypt plantations. Native forests have, so far, remained largely free of invasive exotic insects. The exotic pines, however, have five well-established and significant invasive pest insects: the bark beetles Ips grandicollis, Hylastes ater, and Hylurgus ligniperda (Coleoptera: Curculiondae), Monterey pine aphid, Essigella californica (Hemiptera: Aphididae), and Sirex woodwasp, Sirex noctilio (Hymenoptera: Siricidae), with the latter not yet present in Western Australia (WA). The exotic giant pine scale, Marchalina hellenica (Hemiptera: Margarodidae), was recently detected on pines in Adelaide and Melbourne and is under an eradication program. Many of the established pest species have had classical biological control programs implemented. European house borer, Hylotrupes bajulus (Coleoptera: Cerambycidae), a pest of untreated softwood, is established in areas around Perth, WA, and has been found in dead and live trees, as well as untreated timber. African black beetle, Heteronychus arator (Coleoptera: Scarabaeidae) is a major exotic agricultural and forestry pest in wetter parts of the Mediterranean forest regions in WA, where it was first recorded in 1938. Several other exotic polyphagous horticultural pests are occasionally associated with eucalypts. Australia is the origin of major insect pests on Eucalyptus species grown in Mediterranean regions across the globe. However, populations of these insects are generally effectively controlled by native species of natural enemies in Australia. At least five species endemic to eastern Australia, Gonipterus platensis and G. sp. nov. 2, (Coleoptera: Curculionidae), Paropsisterna m-fuscum (Coleoptera: Chrysomelidae), Phylacteophaga froggatti (Hymenoptera: Pergidae) and Cardiapsina fiscella (Hempitera: Psyllidae), have been introduced to Mediterranean regions of WA, where they initially caused extensive and severe damage to plantations of introduced eucalypt species (predominantly E. globulus) in the region. However, the level and extent of damage gradually decreased, and it has been hypothesised that improved control by endemic natural enemies has occurred.