How to Manage Pests
Pests in Gardens and Landscapes
Centipedes and millipedes are often seen in and around gardens and may be found wandering into homes. Unlike insects, which have three clearly defined body sections and three pairs of legs, they have numerous body segments and numerous legs. Like insects, they belong to the largest group in the animal kingdom, the arthropods, which have jointed bodies and legs and no backbone. Their bodies are covered with a shell-like covering called an exoskeleton. There are several features that distinguish a centipede from a millipede (Table 1).
IDENTIFICATION AND LIFE CYCLE
Centipedes (sometimes called hundred-leggers) are elongated, flattened animals bearing one pair of legs per body segment. The actual number of legs in most species is closer to 30 than to 100. Adult centipedes are usually brownish and more than 1 inch long. The house centipede, a species that often invades buildings, has long legs that enable it to run rapidly. Other species of centipedes more commonly found in gardens may have somewhat shorter legs. Unlike millipedes, centipedes never coil up when disturbed.
Adult centipedes overwinter in secluded moist places. Eggs are usually placed in damp soil in the spring and summer. Some centipede species add segments and legs as they grow; others are born with a complete set. Centipedes require 2 to 3 years to mature and have been known to live 6 years.
Garden symphylans may be confused with true centipedes but are white, less than 1/4 inch long, and have 12 pairs of legs as adults. Symphylans live in damp soil where they sometimes attack underground portions of plants. They are associated with soils that are high in organic matter.
Millipedes (sometimes called thousand-leggers) are brownish, elongated, and cylindrical to slightly flattened creatures with two (more common) or four pairs of tiny legs per body segment. Millipedes don’t really have a thousand legs; even the largest ones have somewhat fewer than a hundred. When they walk, their legs move in an undulating, wavelike manner. Adult millipedes vary from 1/2 to 6 1/2 inches in length. When prodded or at rest, most millipedes curl up. Although there are numerous species of millipedes found in California, three species commonly seen are the common millipede, the bulb millipede, and the greenhouse millipede.
Adult millipedes overwinter in the soil, and eggs are laid in clutches beneath the soil surface. The young grow gradually in size, adding segments and legs as they mature. They mature in 2 to 5 years and continue to live for several years thereafter.
Millipedes may be confused with wireworms and other soil-dwelling beetles because of their similar shapes. Wireworms, however, are click beetle larvae, have only 3 pairs of legs, stay underneath the soil surface, and are more flattened top to bottom.
HABITAT AND IMPORTANCE
Centipedes are usually found in damp, dark places such as under stones, leaf mulch, or logs. Indoors, centipedes may occur in damp areas of basements, closets, or bathrooms, or anywhere in the home where insects occur. During the day they hide in dark cracks and crevices, coming out at night to search for insects to eat.
House centipedes are actually beneficial because they capture flies, cockroaches, and other small household pests. They never damage plants or household items.
When provoked, some large centipedes can inflict a painful bite that may cause localized swelling, discoloration, and numbness. Millipedes normally live in and feed on rotting leaves, rotting wood, and other kinds of moist, decaying plant matter. Generally, their role is a beneficial one in helping to break down dead plant matter. However, when they become numerous, they may damage sprouting seeds, seedlings, or strawberries and other ripening fruits in contact with the ground. When disturbed they don’t bite, but some species exude a defensive liquid that can irritate skin or burn the eyes.
Sometimes individual millipedes wander from their moist living places into homes, but they usually die quickly because of the dry conditions and lack of food. Occasionally, large numbers of millipedes migrate, often uphill, as their food supply dwindles or their living places become either too wet or too dry. They may fall into swimming pools and drown.
Centipedes seldom need to be controlled unless they become a nuisance in the home. Centipedes are predators and generally play a beneficial role in the garden. Their activities should be encouraged in the yard. Reductions in the number of household centipedes occur when their food source—other household pests—is reduced. Airing out damp places may help. Outdoors, centipede control is aided by removing debris as recommended for millipedes. Millipedes also rarely need to be controlled since they do not cause damage indoors and pose a minimal health hazard. Those that stray indoors can be swept out or picked up and released back outdoors. Sealing cracks and other openings to the outside helps prevent millipedes from entering. Usually invasions are over within a few days.
Eliminating moist hiding places around the home will kill or discourage millipedes. Outdoors, this includes removing rotting wood and decaying grass and leaves from around the house’s foundation. This also eliminates millipede food sources. If there is excessive moisture in sub-floor crawl spaces or basements, take measures to dry out these areas. To discourage millipedes in garden areas, reduce mulch and other organic matter and avoid excessive moisture.
Although some pesticides are labeled for controlling centipedes, the use of such products is rarely justified for centipede or millipede control.
Moore WS, Koehler, CS. 1986. Millipedes and Centipedes. UC ANR Leaflet 7172. Oakland, CA.
Shelley RM. 1999. Centipedes and millipedes with emphasis on North American fauna. Kan. School Naturalist. 45(3):1–16.
Flint ML. 2018. Pests of the Garden and Small Farm, 3rd Ed. UC ANR Publication 3332, Oakland, CA.
Pest Notes: Centipedes and Millipedes
AUTHOR: Karey Windbiel-Rojas, UC Statewide IPM Program
Produced by University of California Statewide IPM Program
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