(only 30 years after introduction). The study showed no reduction in fox impacts, and that the project may even have been counterproductive. The evaluation also found that a sustained annual reduction of 65% is required to achieve real declines in red fox populations. Feral cat bounties in Queensland have also been considered to counter the growing problem. The dingo is subject to various controversial bounty systems in Australia. The Australian dingo was itself introduced before European settlement, yet has been considered native of the mainland in most cases both the pure breds and the Dingo-dog hybrids are considered pests to livestock. Invasive insects and terrestrial arthropods Insects are the second costliest class of invasive species in Australia, behind only the mammals. Fire ants in Australia (Solenopsis invicta) are estimated to cost annually, making up 71% of the total costs of invasive insects. This is followed by the Queensland fruit fly (Bactrocera tryoni) making up 12% of the total costs, the Pacific fruit fly (Bactrocera philippinensis) making up 9%, and the bollworm (Helicoverpa) making up 7%. Yellow crazy ants (Anoplolepis gracilipes), black Portuguese millipedes (Ommatoiulus moreletii), Western honey bees (Apis mellifera), and European wasps (Vespula germanica; known elsewhere by the common name "German wasps") are considered to be problematic species. The elm leaf beetle (Xanthogaleruca luteola), discovered in Victoria in 1989 devastates exotic elm trees, themselves imported, and a parasite wasp species as well as the beetle's natural enemy the parasitic fly (Erynniopsis antennata) were in turn introduced in 2001 in an effort to control the pest. Control The red imported fire ant in particular, with its venomous stings, poses a direct threat to human lifestyle. Although control is extremely difficult and spread quickly, the species is currently effectively quarantined to South East Queensland. Both the honey bee and European wasp are well established and now impossible to eradicate in Australia. Honey bees take over potential nesting hollows for native animals and are very hard to remove once established. The yellow crazy ant is currently quarantined to Christmas Island where it has had a significant environmental impact. The primary impact is the killing and displacing of crabs on the forest floor. Invasive birds Introduced birds considered pests include the common myna, the common starling, the spotted dove and rock pigeon (common pigeon). Initially introduced to control locust plagues, the Indian myna breeds prolifically in urban environments in the eastern states. The