Thousands of black millipedes marching into your home after rain? Portuguese millipedes plague Melbourne every autumn and spring. Here is how to stop the invasion.
The Melbourne Millipede Invasion
Few pests cause the sheer visual horror of a Portuguese millipede swarm. After autumn and spring rains, these smooth, black, curling millipedes emerge in their thousands across Melbourne - especially in the outer suburbs and new estates - and march straight into homes at night. They do not bite or sting, but they stain carpets, smell foul when crushed, and can invade in numbers that make a home genuinely unliveable for weeks.
Why They Swarm Into Houses
Portuguese millipedes are an introduced species with no significant natural predators in Australia. They breed in leaf litter, mulch, and garden beds, and two triggers set off mass movement:
- Rain after dry spells - flooding their soil habitat and driving them to higher ground (your house)
- Lights at night - they are strongly attracted to light, streaming toward lit windows and doors in autumn (March-May) and spring
Are They Dangerous?
No - they do not bite, sting, or spread disease. But when crushed they release a pungent yellow secretion that stains carpet, bedding, and walls and irritates skin and eyes. In plague numbers they contaminate food, foul water tanks, and have even stopped trains in Victoria by making tracks slippery. It is a genuine household problem, not just a curiosity.
How to Stop a Millipede Invasion
- Cut the lights - turn off external lights during swarm season, or switch to warm/yellow LEDs which attract far fewer; close curtains so indoor light does not spill out
- Seal the entries - fit door seals and weather strips (millipedes enter under doors), and seal gaps around windows and slab edges
- Remove harbourage - rake back mulch, leaf litter, and dense ground cover from the house perimeter
- Create a physical barrier - smooth vertical surfaces stop them; even a strip of smooth tape on door thresholds helps short-term
- Get a perimeter treatment - a professional residual barrier around the home exterior, slab edge, and entry points kills millipedes as they cross and is the single most effective control during swarm season
What About the Ones Already Inside?
Vacuum them up (empty the vacuum outside - the smell lingers) rather than sweeping or crushing. Millipedes that make it indoors usually die within days from dryness, but during a swarm, hundreds more follow each night until the exterior is treated and sealed.
Timing Matters
The best time to treat is at the first sign of swarming - typically after the first serious autumn rains. Homes backing onto reserves, paddocks, or new estates with fresh landscaping should consider a preventative perimeter treatment each March and again in spring, which also controls other invaders like earwigs, slaters, and spiders.
Under invasion right now? Pest Eraze provides fast perimeter millipede treatments as part of a general pest treatment across Melbourne, from around $179 with a written warranty. Call 0416 528 547.
