When dealing with a pest fly, the recommended course of action is to catch the culprit, put it in a pill bottle, pop that in the freezer, and call a federal biosecurity officer to make a formal ID. But for the average Australian, there’s nothing to distinguish between the genuine invasive sort and stock standard nuisance that bites, loiters and disturbs the peace.
For a creature that spends its time attempting to be seen, heard and noticed, there is very little known about flies in Australia.
“We know the life cycles but we don’t know why it takes two weeks for a blowfly to go from generation to generation and 12 months for a Christmas beetle to do it,” Northern Territory-based entomologist and insect taxonomist Graham Brown told Crikey.
“We know that you’ve got to have the right conditions for insects to really explode in numbers. But for flies, we don’t really know what the up and down drivers are, we don’t know plague numbers, we don’t know the species complex every time there’s a sudden infestation. You’ve really got to sit with a microscope and count hairs.”
There are thousands of fly species that exist in Australia beyond the “few annoying ones” and scant is known about which species go where, which family of flies rule the roost in any given location, what they do, how many flies are in a single space, how many flies are in one generation, what’s the annual churn, how does this compare year on year, what prompts bust and boom… the list of unanswered questions goes on.
Unlike most insect populations where numbers burgeon on the back of big rain or wet climates, Brown said that flies follow no such playbook. While some crave moisture, not all follow rainfall to get their fix. There are species that gravitate towards garbage and waste, and others that run non-functioning FIFO (fly-in and [no] fly-out) services. One fly might clock hundreds of kilometres to seek out an optimal destination, but “why?” and “when?” and “for what?”, Brown says, “We just don’t know”. Perhaps the product of strong winds or strong will, he mused.
CSIRO research scientist and fly expert Keith Bayless said that despite dry conditions, the surplus of flies this year might be a genuine hangover from three years of La Niña or simply a perceived uptick due to human interest.
“If it’s very dry, there’s fewer natural spots for them to be in moisture, so they’re more inclined to come towards humans,” he said, adding that heat may also play a role (albeit unknown) in fly numbers by fast-tracking the standard 10-14 day aging process from maggot to fully-fledged adult.
“Insects don’t develop by a set time, they develop by degree days. The warmer it is, the faster they grow. Again though, there might be more flies out there or we’re just noticing them more.”
In most parts of Australia, Bayless said there’s a dearth of “accurate” fly surveillance and research — either not done well or not done at all. Despite big populations in the NT, he said it’s a particularly neglected region with large reserves where insects “haven’t been surveyed or haven’t been surveyed for a long time”. Even in Darwin, Katherine and Alice Springs, previous research focused on the human-to-fly or agricultural interface for health, habitation and pest purposes, rather than the assessment of species, behaviours, breeding preferences or population levels on a year-by-year basis: “It’s one thing to discover what species are and another to compare them across different regions and across different years.”
Documentation and upload of insect sightings — including flies — by citizen scientists to online platforms like iNaturalist were, Bayless said, helping to bridge knowledge gaps, but he reiterated the need for much more targeted research.
Be that on foot with a butterfly net in hand to sweep vegetation, bright lights and white sheets to act as nighttime drawcards, Malaise traps “named after the adventurer not the emotion of the insect caught in it” that emulate tents, fungus and fruit baits, yellow plastic flowers, or a round of dry ice for blood-sucking specimens, Bayless said there is all manner of methods to attract new species and monitor old ones.
“Living with flies is part of living in Australia. The more we know about them, the more we can control and limit their numbers,” he said.
In central Australia, flies are a genuine environmental factor in any urban dwelling, but Michael Tuckwell, operations manager and senior consultant at Ekistica (part of the Centre for Appropriate Technology), said that beyond the installation of fly screens and nets, insect control was not commonly taken in as part of housing design processes for remote communities. The assumption, he said, was that “minimum building requirements of seals on doors and windows” were sufficient. Beyond that, insects are the responsibility of dwellers.
“Most people just presume that you stick a screen door on and fly screens on a window and it’s done and dusted. But if you talk to most councils and housing contractors, replacing screens, windows and seals are a massive part of their work program,” Tuckwell said.
In remote central Australian communities, he said that “houses get used hard” and in ways not necessarily true to building design. However, misuse of “elegant engineering solutions” to service things that communities “actually need” is “no fault of the end user”, Tuckwell said, but a design flaw indicative of the need to work with inhabitants when designing the homes they’re expected to inhabit.
In one Top End community, Tuckwell said that the housing preference was “Bula Bulas”. These are effectively large tents pitched underneath a wooden-clad platform with an insect net draped over the living space.
“If you’re just building a concrete block house with two windows and a door, all you really need to worry about is making sure those two windows and one door are sealed. That’s very different from something much less durable like a mosquito mesh structure that’s far more susceptible to storm damage and much easier to break or tear,” Tuckwell said.
“But these shelters were introduced by a Traditional Owner and are preferred for this community, so it’s more a question of how you build houses to allow people to manage environmental conditions in a way that suits them.”
