The perception that Australia is overrun with flies is a common experience, often humorously referred to as the “Australian salute” due to the constant hand-waving required to keep insects away from the face. This high density of flies is the result of a specific combination of geography, climate, and a unique biological imbalance. These conditions perfectly align to foster massive populations of certain fly species, turning a natural phenomenon into a constant nuisance for residents and visitors alike.
Identifying the Main Offenders
The most persistent and bothersome fly is the Australian Bush Fly (Musca vetustissima), a native species closely related to the common housefly. This insect does not bite but is strongly attracted to the moisture and protein found in human and animal secretions. Bush flies persistently swarm the eyes, nose, and mouth because they require fluids like sweat, tears, and saliva for nourishment, making them highly irritating to people outdoors.
The other significant group contributing to the fly problem is the Blowflies (family Calliphoridae), which includes species like the metallic-hued bluebottles. Blowflies are larger than bush flies and are notorious for their role in decomposition, as their larvae thrive on carrion, decaying matter, and animal waste. While some blowflies are native, others, like the Sheep Blowfly (Lucilia cuprina), are introduced pests that pose a serious threat to livestock health.
Perfect Breeding Conditions
Australia’s climate and geography create an ideal environment for fly populations to flourish with little natural resistance. A significant factor is the absence of prolonged, harsh freezing winters, which on other continents act as a natural check on insect populations by killing off eggs and larvae. In much of Australia, especially the subtropical north, flies can breed continuously throughout the year.
The large arid and semi-arid inland areas contribute to the problem by providing consistent warmth and dry conditions that accelerate the fly life cycle. Bush flies, in particular, prefer hot, dry weather and can rapidly reproduce when conditions are right. In southern regions, while flies may die out during the cooler months, populations are quickly replenished each spring by immigrant flies blown in on strong, warm winds from the north. A cycle of wet weather followed by warm temperatures also creates a surge in insect populations, providing the moisture needed for initial breeding followed by the heat to speed up development.
The Impact of Introduced Species and Waste Management
The most significant driver of the fly plague is a unique ecological mismatch that began with European settlement. Australia’s native dung beetles evolved alongside marsupials, whose droppings are small, dry, and fibrous pellets that decompose relatively quickly. When European settlers introduced large herds of livestock, such as cattle and sheep, they brought with them enormous quantities of moist, voluminous dung pads.
The native dung beetles were completely unsuited to process this new type of wet dung, which instead lay undisturbed on pastures for months or even years. This created a massive, sustained breeding ground for flies, particularly the Bush Fly. A single cow pat is capable of producing up to 3,000 bush flies in just two weeks, allowing fly populations to surge dramatically across the continent.
To address this biological imbalance, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) initiated the Australian Dung Beetle Project in the 1960s. The goal was to introduce foreign dung beetle species, primarily from southern Africa and southern Europe, adapted to process the moist dung of large ungulates. Over the years, dozens of exotic species were imported and released, with over 20 species successfully establishing themselves across the country. The introduced dung beetles bury the livestock dung within 48 hours, eliminating the fly breeding sites and significantly reducing the number of pest flies. This ongoing biological control effort is considered a major success, with some reports claiming up to a 90% reduction in bush fly numbers in certain areas.