Millipede Facts, Identification and Control
Scientific Order: Spirobolida
Most Common Species: North American Millipede
Scientific name: Narceus americanus
- Size: Varies depending on species; most millipedes commonly encountered in New York are between 1 and 1 ½ inches in length. The relatively common North American millipede may grow up to four inches long, however. Millipede bodies are elongated, rounded, and cylindrical.
- Color: Usually brown, dark brown-red, or black. Legs may appear lighter in coloration than the main body. The North American millipede has large and distinctive red, yellow, or pink edges outlining each of its body segments.
- Despite the name, which is derived from the Latin “thousand legs”, no species of millipede actually has 1000 legs. Most of the millipede species in New York have fewer than 100 legs. Millipede legs are very small and located beneath each of the pest’s discrete body segments.
- Probably the easiest way to differentiate between centipedes and millipedes is by identifying how many pairs of legs the arthropod has per body segment. Centipedes have one pair (two legs) per body segment. Millipedes, on the other hand, have two pairs (four legs) per segment--except on the first four thoracic (the high section, between the head and neck or chest region) segments, where they only have one pair (two legs).
- The North American millipedes’ distinctive, colorful edges give the millipede a black-and-red “ringed” or banded appearance. These edges tend to make it easy to spot each distinct body segment. Other species may not have the same banded appearance across their entire bodies, but most have some kind coloring to mark their edges or legs.
- Most millipedes have a hard, almost shell-like outer exoskeleton on the parts of their back that normally face upward.
- Millipedes eat decaying plant matter and fungi, such as old leaves, dead stems and flowers, mushrooms, and other dying ornamental plants. They also sometimes eat dead and decomposing animals, like worms, snails, and insects. Millipedes are considered highly important recyclers of organic material within their natural ecosystems.
- Millipedes particularly enjoying infesting rotting logs or the soil near rotting trees. Large quantities of rotting wood provide a large food source for millipedes and their offspring.
- Many millipedes seek out fungal growth, so they’re found where fungus and mold thrives: dark, moist environments, such as beneath rocks, leaf piles, thick vegetation, or brick pathways.
- Millipedes may also burrow underground to feed on the damaged root systems of plant life. In some circumstances, this type of feeding may damage gardens or ornamental plants. Millipedes generally only feed on root systems that are already decaying or dying, however.
- Despite their many legs, millipedes move quite slowly. They tend to only move meaningful distances if their food source is disturbed or expended.
- When threatened or disturbed, millipedes defend themselves by rolling their bodies up into a tight coil. Most millipedes, including the North American millipede, also possess tiny pores on the sides of their bodies that secrete toxic chemicals like hydrogen cyanide when the millipede is threatened. These secretions are rarely significantly dangerous to humans, but they might cause allergic reactions or other symptoms in large enough quantities or specific circumstances.
- Millipedes are relatively temperature and humidity-sensitive, and prefer to live in humid, dark environments. The pest often moves in large numbers after a rainstorm or drought changes their feeding environment, rendering it too dry or too wet. In these circumstances, millipedes may infest a building in an attempt to remain within a safe and controlled environment.
- Millipedes range further away from their usual feeding places during fall and mating season. During this period of time they may infest buildings or be spotted on window sills, tree trunks, or door frames. Millipedes climb more than usual during mating season, and may be spotted on any surface up to 6 feet off the ground.
Millipedes undergo a three stage developmental cycle with a “simple” or “incomplete” metamorphosis. Millipede metamorphosis is considered “incomplete” because they do not enter a cocoon “pupal” stage, and so there is not a dramatic difference in morphology or appearance between early stages and final stages.
The three cycles millipedes undergo in their life cycle are:
Millipedes typically begin mating immediately after they emerge from their overwintering shelters in the early spring. After mating, female millipedes construct nests out of regurgitated food and soil. They shape this material into shelter with their legs, and then deposit their egg clutches into it. After the eggs are deposited, the female millipede wraps themselves around the nest to brood the eggs.
It usually takes several weeks for millipede eggs to hatch. Mating and egg laying season continues until temperatures cool in the fall. Newly hatched millipedes are considered the first of several nymphal stages.
Millipede nymphs look similar to their adult counterparts, except that they don’t have as many legs or body segments. Young nymphs eat continuously in order to store the energy required to grow.
As they grow, nymphs must molt by shedding their skin several times. Each time a nymph sheds its skin, it grows new body segments and legs. Millipedes take a quite a long time to mature relative to comparable arthropods. It may take two years or more for a nymph to grow to sexual maturity. Nymphs are considered fully-grown adults when they possess sexual organs and the same number of body segments as adult millipedes.
Adult millipedes are quite long-lived. In a properly humid, dark environment, they may live for another 8 years or more, on top of the 2-5 years they lived as nymphs.
Adult millipedes overwinter by burrowing under soil or seeking shelter in warm, dark environments, such as the underside of rocks or logs.
Signs of Infestation
- Ultimately, millipedes pose little risk to buildings. They do no damage, transmit no diseases, and pose no other threats to people. That also means millipedes can be difficult to identify in your building, however. Most often, millipede infestations are noticed after the millipedes themselves are encountered. Millipedes commonly shelter under boxes or other storage material.
- The secretions produced by threatened millipedes may rarely stain nearby fabrics such as carpet. These stains will be small, vaguely circular, and yellow or brown.
- Typically, millipedes can’t survive inside buildings for long periods of time, because they need more moisture and humidity than a typical building can provide. When millipedes die from dehydration they become “desiccated”. Desiccated millipedes look dried out (obviously), crusty, shrunken, or flakey. Old, desiccated millipede remains may fall apart or become dusty. You may also notice small, broken off millipede legs.
- In some extreme cases, millipedes may damage unhealthy plants outside your building. In these cases, you may notice dead patches of grass, dying ornamental plants, or piles of decaying substances.
Treatment and Prevention
- Because millipedes usually die quickly inside buildings, treatment is rarely required. Vacuum up any millipedes you encounter and dispose of the vacuum bag when you’re finished. If you suspect a larger infestation, check beneath storage materials in basements, crawl spaces, warehouses, and attics.
- If millipedes seem to live comfortably within your building over several weeks or more, it’s probably because your building is producing too much humidity. Seal drafts, repair plumbing leaks, install proper ventilation and drainage, and invest in a dehumidifier to control humidity.
- Cleaning the yard and garden around your building will deprive millipedes of the decomposing material they eat. Rake leaves, remove dead grass and plant material, and dispose of any dead insect or animal life quickly. Ensure that the garbage in your dumpster is transported away from the building weekly, and keep the garbage you place in your dumpster in sealable plastic bags.
- Keep clutter organized and clean to deprive millipedes of their shelter.
- Cornell University Dept. of Entomology Insect Diagnostic Laboratory “Millipedes, Sowbugs and Pillbugs, and Centipedes” fact sheet
- Penn State Dept. of Entomology Cooperative Extension “Millipedes” Entomological Notes
- Study of Northern Virginia Ecology “North American Millipede” page
- University of Kentucky Office for Environmental Programs Outreach Services “North American Millipede” services fact page
- Encyclopedia of Life “American Giant Millipede” entry
- University of Virginia Dept. of Biology “North American Millipede” article by Hazel Galloway
- University of Nebraska-Lincoln Extension in Lancaster County “Managing Centipedes & Millipedes” article by Barb Ogg, Ph. D, Extension educator