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Millipedes, Centipedes, Sowbugs & Roly-Polys - Friend or Foe?

By on June 09, 2011

Some insects you will see out in the garden-but generally not harmful

Centipedes, millipedes, sow bugs, and pill bugs or roly-polys are unusual arthropods. Sow bugs and pill bugs are actually crustaceans (related to shrimp, crabs, and lobsters).

None of these pests transmit diseases to plants, animals, or humans. They don’t damage furnishings, homes, or food—but they can frighten people.

Millipedes

Some folks confuse millipedes with centipedes. These two groups of many-legged, creepy-crawlies belong to different arthropod classes. The obvious differences:

  • Millipedes have 2 pairs of legs per segment, a feature that gave rise to its class name of Diplopoda.
  • Centipedes only have a single pair of legs per segment.
  • Millipedes are vegetarians while centipedes are carnivores.

Get a load of those legs

The name MILLIPEDE comes from the Latin word mille, meaning a thousand, and pedis, meaning foot. While these creatures do have a lot of legs, none actually have a thousand. There are lots of species (6,000+) and the number of legs varies considerably. One source says the highest number of legs known for any millipede is 710.

A millipede can live from 5 to 7 years. They are detrivores, which means they eat dead and decaying plant matter. These little beauties produce new legs almost every time they shed their exoskeletons. They give off a strong-smelling, stomach-irritating chemical when interfered with. If eaten they cause vomiting.

Being vegetarians, millipedes eat plant matter

Some feed on decomposing vegetation and fallen fruit while others will occasionally damage seedling plants by consuming stems and leaves. They eat all kinds of potatoes, flower bulbs, and tubers. They live in the garden in areas of moist mulch, compost, and lawn thatch. The females lay between 50 to 100 eggs a year and live for about 3 years.

Millipedes have a tendency to wander indoors in the late fall, in search of somewhere to overwinter.

BLACK MILLIPEDE (Tachypodiulus niger) looks like a length of black, armoured pipe and coils stiffly like a watch spring.

SPOTTED MILLIPEDE (Blaniulus guttulatus) has a row of reddish spots along each side of its yellow body.

Centipedes

Centipedes are worm like, with flattened bodies.  They belong to a group called Chilopods. Color can be brown, gray, red, or greenish-blue. with many body segments. Most of the body segments have one pair of legs. Centipedes are fast runners and may vary in length from 1 to 6 inches. They have one pair of antennae or “feelers” that are easily seen. Centipedes have poorly developed eyes and are most active at night. They are predators and feed mainly on insects and spiders.

Best rule of thumb? Never handle centipedes.

Centipedes do have the first pair of appendages modified into claws, which can inject poison through their venom glands, which they use to immobilize their prey. The larger centipedes can bite people and they emit an irritating fluid that can cause an allergic reaction.

Centipedes prefer moist, protected habitats

They are delighted with spaces under stones, rotted logs, leaves, or bark. They spend the winter as adults and lay eggs during the warm months. Indoors they may be found in closets and bathrooms where there is high humidity.

They usually lay 15-55 eggs clustered together, although the eggs of some species are laid alone. Eggs are usually laid in soil and covered by a sticky substance; they hatch soon after they are deposited. The female will usually guard the eggs and the newly hatched young. Young centipedes closely resemble the adults and require 3 years to mature. Centipedes may live up to 6 years.

Sow bugs & Pill bugs

Sow bugs and pill bugs (both also known as woodlice) are terrestrial crustaceans, and are related to lobsters, shrimp and crayfish. They are the only crustaceans that have adapted to living their entire life on land and they still have gills.

The habits, biology, and control of sow bugs and pill bugs are similar. Both animals are slow-moving, crawling arthropods. They need a moist environment and are most active at night. During the day they rest under trash, rocks, boards, decaying vegetation, or just beneath the soil surface.

Pill bugs roll up, sow bugs can’t

The main differences between a sowbug and a pillbug:

  • The sowbug possesses two tail-like appendages, seven pairs of legs, and well-developed eyes. They are incapable of rolling into a tight ball.
  • Pill bugs or “roly-polys” lack the tail-like appendages and can roll into a tight ball or “pill” shape when disturbed.

In both species breeding can occur throughout the year in mild climates. The female carries the eggs in a brood pouch on the underside of her body, with up to 200 eggs per brood. The eggs hatch in 3 to 7 weeks and the young remain in the pouch another 6 to 7 weeks.  Some species produce only one brood per year, but others may produce 2 or more. Individuals may live up to 3 years.

What they eat

At night they venture out and feed on decomposing organic material. They will feed on the tender foliage, stems and roots of young garden vegetable transplants, seedlings, and bedding plants. They also rasp the outer skin of cucumbers lying on the ground in gardens,  causing fruit to be deformed and blemished.

Mainly a nuisance, pillbug and sowbug control in the garden is not always necessary, as they cause little harm to plants. In fact, most gardeners do not categorize them as pests, but think of them as beneficials for converting decayed vegetation into humus.

However, if you notice pill bugs or sow bugs feeding on tender seedlings, you can refer to our list of Insecticides for controlling them.

Ways to Control

Unless these guys are causing damage to your plants, they are ok to not bother them. But if you feel they are causing damage, look for natural insecticides that are labeled for these pests.

Here are a few methods that can be tried to control millipedes, centipedes, sow bugs, and pill bugs in the garden organically without the use of pesticides:

  • Reduce moist areas in the garden where eggs overwinter.
  • Rake out old mulch under plants and replace it with fresh mulch or straw.
  • Move piles of leaves to a compost pile away from areas you want to keep insect free.
  • Aerate your lawn to reduce thatch that could provide a damp home.
  • Pour wood ash into their nest area to dry out soil and create an uninhabitable area. Be careful because a large amount of wood ash is toxic to your soil and garden.

Chickens are great biological control for millipedes, centipedes, sow bugs, and pill bugs, as well as a wide variety of other pests. Chickens are voracious eaters and spend most of their day wandering around looking for little moving critters they can eat.

Control Millipedes, Centipedes, Sow bugs and Pill bugs Indoors

A heavy infestation indoors usually indicates a large population outdoors. To keep millipedes, centipedes, sowbugs and pillbugs from coming indoors, move their habitats (compost piles, firewood, and stones) away from the house. Items that cannot be removed should be elevated off the ground. Create a band of gravel between your house foundation and flowerbeds.

All these arthropods require moisture and do not survive indoors for more than a few days. Sweep them up with a broom or vacuum them. To combat serious infestations, seal cracks in your outside foundation, and around the bottoms of doors, and basement windows.

Not So Bad

Though they may “freak us out”, millipedes, sow bugs, and pill bugs assist us by eating decomposing matter. The centipede eats aphids and other soft-bodied insect pests.  Unless they are actually damaging your young seedlings, it is not necessary to do anything to control their populations.

Some folks have taken to making millipedes pets!  There is always something new and fascinating when it comes to nature.

Photo Credits

  • Armadillidium vulgare by Joseph Berger, Bugwood.org
  • Porcellio scaber by Joseph Berger, Bugwood.org

  Comments (15)

S

i found two clusters of little tiny looked like baby centipedes all clustered together to look like a big slug. what are these things if they are not centipedes?

Posted by sheila vogel on Jul. 14, 2013 at 7:00:24 PM

Sheila, It is hard to say without a photograph, but some species of centipedes do lay eggs in clusters. Perhaps you saw a recently hatched cluster of eggs? One other way of identifying the insects is to consult your local Master Gardeners who are very familiar with the garden insects in your county. Here’s how to find the closest Master Gardeners (volunteers) http://www.ahs.org/gardening-resources/master-gardeners

Posted by GrowOrganic.com on Jul. 15, 2013 at 4:28:20 PM

H

Very informative. I’m not so freaked out now. We recently bought a house (3 weeks ago), and used lawn weed killer today finally because it’s creeping charlie crazy out there. Tonight it’s going to frost I guess, so I’m not sure which caused the millions of millipedes to run to the patio and shop and even in the laundry room, but I was running around spraying and squishing… now I know they aren’t going to bite us, and I turned on a fan in the shop. Thanks!

Posted by Heidi on Sep. 16, 2013 at 1:23:41 AM

Heidi, That’s a lot of house guests all of a sudden!

Posted by GrowOrganic.com on Sep. 18, 2013 at 3:02:31 PM

M

I’m a balcony gardener and have two huge containers for my zuchini. This year, I didn’t have any problem with any sort of pest, thanks to the centipedes that live in there, I guess. Problem is that I found that the population is seriously getting out of control. Can I do anything about that? Do you have an idea?
Any help will be appreciated,
Maia

Posted by Maia on Sep. 23, 2013 at 6:48:58 AM

Maia, The centipedes should be eating other insects, not your zucchini, so an overpopulation should not harm your garden. Clear the mulch off your zucchini pots so that they don’t have many places to live. If there are not enough insects to hunt then the centipede population will adjust itself.

Posted by GrowOrganic.com on Sep. 30, 2013 at 11:09:13 AM

C

I have a large problem will pill bugs inside my home. I am noticing a smell in my livingroom that is causing health problems and I see mounds of pill bugs when I move my furniture. can they cause allergy problems I have to become worse?

Posted by crystal on Jun. 11, 2014 at 7:51:01 AM

Hello Crystal,

That does sound like a problem. Since the pill bugs eat decaying organic matter that means their might be something organic decaying somewhere in your living room (perhaps the source of the smell). I would recommend doing some serious cleaning and see if you can find the pill bug food source.

Posted by GrowOrganic.com on Jun. 11, 2014 at 9:34:08 AM

C

Hi there,
Great to see your info on these mostly OK garden critters.
I am noticing a rather large amount of a tiny surface/ soil bug. its about 1/2 in long often, dark, and many legged. Possibly baby millipedes? I find them under pots a lot and am concerned they could be eating roots. They are especially many in areas I am having a hard time getting new plants established! I only see a large millipede hiding in our mulch piles on rare occassion so I don’t think the tiny ones are babies. So far I can’t find anything about them on the net. Your site looks the most promising. Do you know anything about these guys?
THANKS so much ahead for your help!
Candace

Posted by candace stolley on Jan. 07, 2015 at 1:15:12 PM

Not actually seeing the bug I cannot give you much advise. Try catching some and taking down to a Master Gardener or local Ag Advisor to see if they can identify the critters.

Posted by Suzanne at Peaceful Valley on Jan. 09, 2015 at 1:20:03 PM

J

I have 2 patchouli plants, together in a large pot. Its winter here in maryland, so all of my tender perenials and tropicals have been brought indoors. While everything else is thriving, thanks to grow lights and dedication, but patchouli just seems to be slowly dying. Outside it was very healthy and growing like crazy.
The other day i noticed little grey pill bugs in the pot, among the soil. I know they eat dead matter, so i have been very careful to collect any of the dead leaves and such which fall in. Could they possibly be eating the roots of my patchouli???
I plan to repot both of them separately, cleaning the roots and plants in the process. Will this help?
Thanks in advance! Please help me save one of my favorite plants!!!

Posted by Joshua on Feb. 14, 2015 at 10:27:03 AM

If they do not have any dead matter to eat, they can feed on young tender roots. Repotting may not do anything but getting rid of the pill bugs that are present. The following link is a list of organic pesticides listed for pill bugs, http://www.groworganic.com/weed-pest-control/organic-pest-control.html?solution_pest=273

Posted by Suzanne at Peaceful Valley on Feb. 16, 2015 at 9:45:24 AM

M

Just wondering if millipedes are harmful to my worm farm? I seem to have quite a few suddenly, and wonder if their wee is just as good as worms, or if I should try to get rid of them? Thanks.

Posted by Martha on Mar. 19, 2015 at 5:18:54 PM

Millipedes eat decaying matter and should not be a threat to your worms. I would not worry about trying to get rid of them since they will help break down the decaying scraps.

Posted by Suzanne at Peaceful Valley on Mar. 25, 2015 at 11:26:21 AM

L

Pill bugs are eating my seeds before they can germinate.  Thanks for the info.

Posted by laura on Apr. 20, 2015 at 6:47:03 AM

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