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written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Early each spring I get calls about a variety of creepy and crawly creatures that show up in yards, gardens, and sometimes even in garages or houses. The most commonly encountered creatures are dark grey to black “worms” that appear in large numbers along sidewalks and in landscape beds. Most people don’t want to get up close and personal enough to describe these worms, so all they can tell me is that they curl up when touched or dead.

Although I have a good idea of this “worm’s” identification, I usually ask folks to bring me a sample because it’s very difficult to accurately identify insects and their relatives over the phone. Invariably, the “worms” turn out to be millepedes. Millepedes are not insects or worms, but are considered wormlike arthropods. Their elongated body is roundish and segmented with each segment, except for the front ones, having two pairs of legs. With four legs per segment it’s no wonder that they were named millepedes which means “a thousand legs”… although they fall far short of actually having that many legs.

There are different species of millepedes found in the garden, some are small ones only measuring a few millimeters in length and others grow to an inch or more long. Typically, the ones found in area gardens are brownish to dark grey and one half to three quarters of an inch long. As arthropods, their hard exoskeleton makes them “crunchy” instead of squishy when crushed.

With so many legs you would think that millepedes would be fast moving, but they’re not. They don’t need to be fast since their food isn’t hard to catch. Millepedes are “recyclers” feeding on decaying organic matter. They’re usually found where there is some type of moist decaying plant refuse… in compost, leaf piles, thatch, manure, and soils high in organic matter.

Most of the year, you may encounter one or two millepedes here or there in the garden, but in the spring and sometimes in early fall massive numbers emerge prompting calls to me asking what to do about all these “worms.”

When a sizable group of millepedes emerge in the spring or fall, experts tell us that there are several possible causes. They say that the most likely cause is population pressure, where their numbers have built up to high enough levels that they’re competing for food and habitat, prompting an exodus to find a new place to live.

The experts also note that there may be other reasons for the appearance of massive numbers of millepedes. If their habitat is destroyed or abruptly changed in some way, they will move. Warm spring weather may dry up their habitat and because they need moist conditions to live, the millepedes will suddenly move elsewhere. While they do require moisture, excessive moisture or standing water is a also a problem that requires a change of address. Even spring garden cleanup, can result in the destruction of millepede habitat.

When you encounter these many-legged recycling arthropods, you need not be concerned. They should be considered beneficial in the garden and are only a nuisance when suddenly present in large numbers. If masses of millepedes appear, the best solution is to sweep them up or use a shop-vac for cleanup. If you’re bothered by mass migrations of millepedes once or more a year, consider eliminating places around your home where they have food and moisture.

Published: 4/9/2011 10:16 AM



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