The black Portuguese millipede, Ommatoiulus moreleti, is a native of Portugal and was accidentally introduced to Australia, first appearing in South Australia in 1953. They have since invaded all the southern mainland states.They are attracted to light and will enter buildings at night, although once inside they do not breed and will eventually die.
While there is no evidence they affect human health, they can occur in plague numbers, and can contaminate food and infest carpet and bedding. Portuguese millipedes are herbivorous, which means in plague proportions they may also destroy seedlings and fruit and vegetable crops.
When disturbed a millipede may release a pungent and distasteful yellowish secretion which discourages predators, such as birds. Note: the secretion may stain skin or clothes and is extremely irritating if rubbed into the eyes. However as it is composed of organic chemicals called quinones, it quickly breaks down in water.
Mature black Portuguese millipedes are smooth and cylindrical, 20-45 mm long and slate-grey to black in colour. Juveniles are light brown and striped. Juveniles hatch from eggs in the soil and reach maturity in two years.
During hot dry weather they will hide in the soil, however rain in spring and particularly in autumn will stimulate activity and breeding.
Portuguese millipedes are attracted to light. If you are able to do so, turn off any external lights which are close to your house or other buildings and minimise any escape of light by closing curtains and blinds. Use weather-strips on doors as good door seals will also help prevent entry into the home.
While compost is good for gardens, it also allows higher populations of millipedes to breed. If you can, reduce the area covered by organic matter such as compost, leaf litter and mulch as it decreases a source of food and shelter. Don’t forget your gutters.
While some spiders, beetles and scorpions will eat millipedes, they will not significantly reduce numbers.
A smooth vertical or rounded barrier can stop millipedes from entering buildings as they are unable to gain a foothold. The barriers can be fixed to walls, below doorsteps, window ledges and vent bricks (make sure you keep them clean and free of vegetation). A barrier must be continuous with no breaks (unless placed under doorways).