Portuguese Millipedes are a seasonal pest and mostly invade in spring, autumn and after heavy rains. Millipedes do not contain a bite or sting but can produce a staining fluid that is repellent to some insects and birds, thus they have very few predators.
Millipedes are slow crawling and appear to have hundreds of legs. They are 20-45mm long with 50 body segments when fully developed. The adults range in colour from slate-grey to black. The juveniles are light grey/brown, often with a darker stripe along each side.
Millipedes live in undisturbed decomposing material, leaves, mulch and anything that's moist. They get their nutrition from these locations. When they breed, the eggs hatch and larvae will start feeding right where they emerge. This leads to large populations or nests which can be in the hundreds. Millipedes will remain feeding as long as there is a food source to support the nest.
Portuguese millipedes are not harmful to animals or humans, but they can be a significant domestic nuisance when they invade homes and gardens in their thousands. They are attracted to light at night and seem to also be attracted to homes with light coloured walls. Although Portuguese millipedes do not breed inside homes they can invade in substantial numbers.
Treatment to prevent the invasion of Portuguese millipedes involves applying a barrier treatment to the exterior of the building, which will kill the millipedes on contact. Chemicals can be applied to outside walls, paths and garden beds or other areas where millipedes are evident.