Millipedes, sowbugs, roly polys, pill bugs and centipedes. These are all multi-legged non-insect type creatures that inhabit the same type of wet, highly mulched areas around the home.
In the spring and summer these creatures sometimes migrate by the thousands, marching toward and into your house. No one knows for sure what causes these migrations. The best guess is that it's a combination of temperature and humidity. Millipedes and their kin like secluded damp areas where they can feed on decaying plant material. But too much or too little moisture in their environment can make them leave these areas in huge numbers.
1. De-thatch lawns---Millipedes thrive in the dense upper thatch of grass.
2. Mow lawn close---This allows the lawn to dry out.
3. Remove debris--Millipedes live under boards, rocks, mulch, etc.
4. Water the yard in the early morning---This lets the yard dry before night.
CHEMICAL MILLIPEDE CONTROL
Because millipedes are not insects, the standard insecticides such as diazinon, dursban, malathion, etc. have little effect on them. The best pesticide to use is Ficam W, but this is no longer available. The next best thing to use is Demon WP. It will give you excellent control of millipedes and their kin. Spray areas where the millipedes are thickest and also spray 3 feet completely around the house and 3 feet up on the foundation of the house to prevent entry of the millipedes inside.