Winter is coming, but it's not only farmers who welcome the wetter months; the arrival of the first rains are celebrated by hordes of Portuguese millipedes.
Individually, the tiny black creatures are relatively benign, but their infamy comes from the sheer quantities in which they descend on unsuspecting households.
Evolutionary biologist Nadia Sloan said as the name suggested, Portuguese millipedes were not native to Australia but had come from south-western Europe.
"The first recorded instance of them being here in Western Australia was in the late 1980s … they are in the Perth metropolitan area and have spread all through the south-west of WA," she said.
Dr Sloan said Portuguese millipedes, like most millipede species, preferred damp, dark areas, which is why their arrival coincided with the first rains of the season.
"This is the time of year that they are starting to breed, so they're on the move, walking around and looking for mates," she said.
"If you've ever touched a Portuguese millipede and noticed that they leave like a yellow kind of staining, that's the toxin coming out as a defence mechanism … to make them taste pretty bad to any potential predators out there."
Dr Sloan said although limited research had been conducted into Portuguese millipedes in WA, she believed their abundance in certain areas could be due to a higher tolerance for environmental pressures than their native counterparts.
"[Portuguese millipedes] are the most noticeable millipede in the environment, but there are a lot of native species in Western Australia that don't get so much attention because … you don't really see them around people's houses."
Dr Sloan said the plague proportions of this particular pesky species should not put people off millipedes generally.
"[Millipedes are] fascinating little creatures and really important for the environment in terms of decomposing leaf litter and soil turnover," she said.
Plague proportions
Katanning resident Kirsty Bride said she first noticed the Portuguese millipedes about six years ago.
"[They've] just been getting worse over the years, and this year seems to be worse than any other year … it's just thousands," Ms Bride said.
"They sit at the doorstep … all my doors have doorstops covering them to stop [the millipedes] coming through.
"They just keep walking around until they can find a way to get into the house … they come inside and they die, and then they turn crunchy."
Armed with a vacuum cleaner and tissues, Ms Bride does a daily sweep of the house to clean up the invading armies, but despite her best efforts, she has not yet found a way of safeguarding the house.
"We do get our house sprayed for bugs and it works for everything else but these Portuguese millipedes."
Ms Bride said she took to her local community Facebook page for advice on the issue.
"We've got some bags of salt … so we'll try putting salt around the doorways and around the perimeter of the house itself," she said.
"Somebody did say just a bucket of water with a light beside it and they'll just go into there, and then you've got to empty them out.
"Otherwise, we'll just go to the next level and try [insecticides]."
WA horticulturalist Steve Wood said he was familiar with the plight of households suffering from Portuguese millipede invasions.
"They infiltrate the household… I've known people that have been laying in bed and they're fallen down from the ceiling and through the air-conditioning ducts," he said.
Mr Wood said Portuguese millipedes were attracted to light, so keeping household lights to a minimum at night was essential to keeping the pests at bay.
"Make sure you turn off lights on verandahs and porches. If you've got lights on inside the house, pull down the blinds so that you're not [shining light] outside," he said.
Mr Wood said insecticides were another option to manage , but warned proper measures such as gloves and masks should be worn if toxic chemical products were being used.
Dr Sloan advised those considering mitigation by chemical means that insecticides rarely affected only the targeted species.
"You're also going to start potentially harming other invertebrates and insects in the environment that are really beneficial," she said.
"[Portuguese millipedes] live and breed in moist, damp soil … so try to keep compost and leaf litter clear from around the perimeter of your home.
"There are a few options out there to try and deter them from entering the house [before you use insecticides]."
