Introduced Species
European wasp (Vespula germanica) are an introduced species and therefore does not have natural predators in Australia to keep number of these wasps low.
Mass attack when disturbed
European wasps can sting multiple times. A wasp can call other colony members using a scent chemical (pheromone) to help defend the nest from a potential threat.
Massive nests
Because of Australia’s warm climate, nests can grow over a number of seasons. This can result in giant and potentially dangerous nests of over 100,000 wasps.