Centipedes and millipedes are generally beneficial creatures.
Centipedes feed on soil-dwelling mites, insects, insect larvae, baby snails, and slugs. (They paralyze small insect prey with venomous claws.)
Millipedes feed on decaying plant tissue and fallen fruit.
Together centipedes and millipedes help break down organic matter enriching the soil by helping to create humus.
Sometimes centipedes and millipedes can be pests. Centipedes also eat living plant tissue and earthworms. Millipedes sometimes feed on plant roots, germinating seeds, and seedlings.
Centipedes and millipedes are close relatives of insects, but they are not insects. Centipedes belong to the class Chlopoda, not Insecta; millipedes belong to the class Diplopoda, not Insecta.
Centipedes look like segmented 1-inch worms with 30 or more legs. They are brown, flattened, have a distinct head, and one pair of jointed legs per segment. They hide during the day under garden debris and are active and feed at night.
Millipedes are up to 2 inches long. They have hard-shelled, cylindrical, and segmented bodies with two pairs of short legs per segment. Millipedes can have up to 400 legs (not 1,000 as their name implies). They are often found coiled in the soil during the day and are active at night.
Centipedes are fast-moving. Millipedes are slow-moving.
Centipedes can be pests when they feed on the roots of asparagus, cucumber, lettuce, radish, and tomato. Millipedes can be pests when they eat the roots of beans, cabbage, carrots, corn, potatoes, strawberries tomatoes, and turnips.
Centipedes and millipedes overwinter as adults in the soil. In spring they lay clusters of translucent eggs. Nymphs are smaller versions of the adults. There are many generations of centipedes each year. There is just one generation of millipedes each year.
To prevent centipedes and millipedes from eating the above-ground portions of plants, sprinkle wood ashes, diatomaceous earth, or cinders around plants, seedlings, and near rows of germinating seeds.
Centipedes and millipedes are found throughout North America.