Bugs! Creepy Crawlies! What’s in my Worm Bin?

In addition to the millions of microorganisms working to help your worms digest and compost your waste, there are larger organisms that will appear in your worm bin. Here is a guide to critters you might find, their relationship to your worms, and whether or not (and how) to get rid of them.


Potworms


Pot Worms
Potworms are common in worm bins and enjoy slightly acidic conditions.

Potworms are small white worms commonly found in soil. They can develop into massive populations, especially in compost piles or in earthworm farms. They’re scientifically known as enchytraeids (enn-kee-TRAY-ids) and are segmented relatives of the earthworm. They are often thought to be baby red wigglers, but baby red wigglers are reddish even when they are tiny.


The name “potworms” comes from the fact they inhabit the soil in pots and containers. There is some unnecessary worry that overpopulation will choke out the worm population. That is typically not the case as potworms and a host of other creatures, including those that cannot be seen except under a magnifying glass or microscope, reside peaceably with earthworms, often in great numbers.


When a potworm invasion occurs, they can number as many as 250,000 in a ten-square-foot area. Adults measure about a quarter of an inch, and can literally appear to be in the millions in comparison to your red wiggler worm population. Potworms tend to congregate together under food.


Potworms feed on the same type of litter as earthworms and inhabit rich organic environments such as a compost heap or worm composter. They are efficient at aerating soil and breaking down just about any organic material. This species prefers an acid environment that is moist. Commonly they will spring up (seemingly out of nowhere) when lots of acidic materials are added to the bin, or when starchy materials are added and allowed to ferment. If the bin is too dry, they will die.


The easiest way to reduce potworm populations is with bread soaked in milk. They will flock to a piece of soaked bread and can be lifted out and destroyed in large batches


Just as potworms won’t harm other living worm species, they do no damage to living plants. The only possible problem that could occur with potworms in a worm bin is if their population grows so large that they compete for food with the red wiggler composting worms. However, this rarely happens and potworms generally help with the composting process.


Earwigs


Earwigs are outdoor insects usually found under mulch, logs or dead leaves. They both need and are very attracted to moisture. Earwigs are rapid runners, and are easily identified by the prominent pincers on the end of the abdomen. The common earwig is a light, reddish brown flattened insect, up to one inch in length. Most species of earwigs are scavengers that feed on dead insects and decaying plant material. Some species are predators. Earwigs may try to pinch if handled carelessly, but are harmless to people. They are not harmful in a worm composter but may eat some of the earthworm food.

Earwig
Earwigs can be identified by their pincers on the back of their abdomens.

Beetles


The most common beetles in compost are the rove beetle, ground beetle and feather-winged beetle. Feather-winged beetles feed on fungal spores, while the larger rove and ground beetles prey on insects, worms, snails, slugs and other small animals. Rove beetles are the most common group of beetles found in composting bins. They are slender, elongated beetles with wing covers (elytra) that are much shorter than the abdomen; over half of the top surface of the abdomen is exposed. Their tail often bends upwards and they can be mistaken for earwigs. Most rove beetles are black or brown. Most rove beetles are medium sized beetles; a few species are up to one inch long. Rove beetles are active fliers or runners. When they run they often raise the tip of the abdomen. Rove beetles don't sting, but can give a painful bite. They are found in or near decaying organic matter and feed on other insects such as fly maggots.


Beetles are not harmful in the worm composter.

Rove Beetle
The rove beetle is the most common beetle in worm bins.

Springtails


Springtails are tiny, wingless insects, usually white in color but may also be yellow, gray, red, orange, metallic green and lavender. They feed on mold, fungi, bacteria and decomposing plant material so they are harmless to earthworms. Springtails can “jump” about 75 mm. They have a tiny spring-like structure under their bellies that causes them to jump when disturbed. Springtails are most numerous in wetter bedding, while numbers decrease as the bedding dries out.

Springtales
The springtail is usually white and enjoy wet bedding conditions.

Although they have on occasion been observed to eat dead or weak worms, springtails are primarily a nuisance because they eat the worm’s food and can, when the populations are big enough, drive the worms deep into the beds and keep them from coming to the surface to feed. One deals with them the same way one deals with mites. (See below)


Mites


Mites are the most common pests to show up in your vermicomposter. Most worm beds usually contain several species of mites. Earthworm mites are small and are usually brown, reddish or somewhere in-between. They tend to concentrate near the edges and surfaces of the worm beds and around clusters of feed. They are not known for attacking the earthworms but do eat the worm’s food. When the mite population is too high the worms will burrow deep into the beds and not come to the surface to feed, which hampers worm reproduction and growth.

Springtails
Mites are usually red or brown and enjoy wet bin conditions.

Mites can compete with the worms for available food if the population spirals too high. High mite populations usually result from:


  • Feeding the earthworms overly moist garbage and vegetable refuse as feed.
  • Over-watering. Keep the beds damp but not wet.
  • Poor bed drainage. Ensure that there are adequate drainage holes at the bottom of your worm bin or housing.

Remember, the same conditions that ensure high worm production will be less favorable to mites. If you find your worm farm overrun by mites, expose the beds to the sun for a few hours. Cut back on water and feed and then, every 1 to 3 days, add calcium carbonate. Add additional shredded paper or coconut coir to absorb any excess moisture. Drain off any liquid that has collected in the base and check to make sure the spigot is not plugged.


Fruit Flies


The worm bin is the perfect fruit fly and fungus gnat haven because of the abundance of organic matter and the moist conditions. Fruit flies are not actually flies because they have multiple wings. Fruit fly invasions are a fact of life in the worm composting world, and they can be unpleasant guests, but they are NOT harmful to your worms or in the composting process. They are simply a nuisance. Fruit flies can be a problem year round but are especially prevalent in the summer and fall because they are attracted to ripened or fermented fruits and vegetables. Fruit flies reproduce quickly and abundantly – each adult can lay 500 eggs in their lifecycle, which is about a week long. The eggs attach to the surfaces of fruits and vegetables, and that is how they travel into our homes. Please see Fruit Flies: Prevention and Control in a Worm Bin for tips and tricks on ridding your worm composter of these nuisances.


Centipedes


Centipedes resemble millipedes, but their bodies are more flattened and less rounded at either end. Centipedes have one set of legs per segment on the bodies and a pair of pincers which originate behind the head. The centipede is generally more reddish than the millipede.


Centipedes are fast moving predators that will kill worms and should be removed. The stingers behind their head possess poison glands that they use to paralyze small earthworms, insect larvae and small insects and spiders. The only way to control centipedes is to remove them by hand which should be done carefully. They will use the pincers to sting.

Centipede
A centipede has one set of legs per body segment and a slightly flattened body.

Millipedes


Millipedes have wormlike segmented bodies with each segment having two pairs of walking legs. Colors range from black to red, but those species found in the worm bin are commonly brown or reddish-brown. Millipedes are vegetarians that break down plant material by eating decaying plant vegetation. They will roll up in a ball when in danger. They are harmless to earthworms. Millipedes move much more slowly than Centipedes and have a rounder body.

Millipede
A millipede has a round body and has two pairs of legs per body segment.

Sow Bugs & Pill Bugs


Sow Bugs, also known as a “wood louse” are fat bodied crustaceans with delicate plate like gills along the lower surface of their abdomens which must be kept moist and a segmented, armored shell similar in appearance to an armadillo. They are brown to gray in color and have seven pairs of legs and two antennae. They move slowly, grazing on decaying vegetation. They shred and consume some of the toughest materials, those high in cellulose and lignins. Sow bugs are usually found in the upper areas of the worm composter where there is an abundance of unprocessed organic matter. They are highly beneficial in the worm composter but can harm young plants.

Sow Bug
Sow bugs eat some very tough materials and can help your worms with hard-to-consume items.

Pill bugs, or “roly polly bugs” look similar to sow bugs but roll up in a ball when disturbed.


Slugs & Snails


Slugs and snails can be found in your vermicomposter. While they will not harm the worms they will eat any fresh kitchen waste in the composter. The biggest detriment is the eggs they lay. The eggs can be transferred into your plantings in the compost providing them with a meal of succulent young plants.


It is best to remove any slugs or snails you find immediately. If they become a problem you can make a slug trap as follows:


Cut several 1 inch opening in the sides of a clean, covered plastic container. Sink the container into the bedding of the top tray of the worm composter so that the holes are just above the level of the compost. Remove the lid and pour in ½ inch of beer or a yeast mixture of 2 tablespoons flour, ½ teaspoon baker’s yeast, 1 teaspoon sugar, 2 cups warm water. The slugs will be attracted to the beer or yeast mixture, fall in and drown. Check the container regularly.

Slug
Slug eggs can be transferred in finished compost and after hatching, the young slugs can destroy young plants. It is best to remove slugs from your bin.

Ants


Ants are attracted to the food in a worm bin. They feed on fungi, seeds, sweets, scraps, other insects and sometimes other ants. Try not to spill anything near your bins and clear away any spillage as soon as it is spotted. The presence of ants is an indication of dry bedding. Moisten the bedding and turn it with a trowel to disrupt their colonies and most ants will find some place else to live.


One way to keep ants out of your worm composter is to put each of your bin’s legs in a dish of water that has had a drop of dish soap placed in it to reduce the surface tension of the water. This prevents the ants from walking across the water. Alternatively, most of the garden centers sell ant goo, a sticky substance that is painted around the stems of rose bushes to trap ants. It is eco friendly as it doesn't contain any insecticide poisons.

Ants
Ants are attracted to a dry bin, so sprinkle water on your bedding or add moist materials to discourage ants.

If all else fails and the ant invasion has already become serious, you can dust the area around your beds with pyrethrum dust or douse the ant nest and the trails leading to your bin with a granular insecticide, or use commercially available ant traps, which contain slow release poisons that the ants take with them back into their nests. Please be sure not to use any insecticide on the actual worm bed soil or you will kill your worms. If ants are already established inside the beds soak the section they are in with water and they will usually go away.

If you don’t want to go to that much trouble, take heart! The ants don’t bother the worms and they actually benefit the composting process by bringing fungi and other organisms into their nests. The work of ants can make worm compost richer in phosphorus and potassium by moving minerals from one place to another.


Blow Flies & House Flies


Excess flies buzzing around your worm bins or worm farms are usually the result of having used meat, greasy food waste, or pet feces as feed. They spread disease and make life miserable for the worm farmer and his family. They can also result in maggots if the beds aren’t properly sealed. If your farm is kept indoors or under some sort of shading – as it should be – then you can hang up some fly strips, which will draw them away from the farms. Again, a properly maintained worm farm will normally not stink and therefore not attract flies.

House Flies
The presence of house flies in your bin can indicate improper food that has been added.

Soldier Flies


Soldier flies are true flies that resemble wasps in their appearance and behavior. Adult flies vary in color from black, metallic blue, green or purple, to brightly colored black and yellow patterns. The larvae of the fly are a type of small maggot that feeds exclusively on putrescent material. They are often found in worm composters but are not a real threat to the worms. They do not attack them or compete with them for food and may in fact complement the compost worms activities. Like the vermiculture worms their feces make excellent compost. They can best be kept out of the worm composter by not using meat and fatty waste and by keeping the moisture on the dry side. Make sure that there is a good cover of bedding material over the feeding area.

Soldier Fly
Soldier fly larvae and adults are not harmful to your worm bin.

These remarkable creatures, unlike the common housefly, do not spread bacteria or disease. In fact, the larvae ingest potentially pathogenic material and disease-causing organisms and thus render them harmless. Moreover black soldier flies exude an odor which positively discourages houseflies and certain other flying pests. When the larvae reach maturity they leave the feeding area to pupate. The adult fly is nocturnal and characterized by very fast and rather clumsy flight. It has no mouth and cannot bite or sting.


Soldier fly larvae are harmless to you, your worms and your plants. They are very good decomposers and, if allowed to stay in your vermicomposting system, will help to recycle your waste. Just be sure that your worms get plenty to eat as well. The soldier fly manure does make good worm feed as well.


Maggots or Larvae


The most common type of maggots found in a worm bin are grey-brown and about 1/2" long. These are the larvae of the soldier fly, a large pretty, blue/black fly. These larvae are attracted to compost piles and to the worm bin, and will not harm you or your worms. In fact, they are good decomposers and, like the redworms, will produce a high quality casting.


If you haven't added animal proteins, and don't have any foul odors in the bin, then in all likelihood the maggots you are seeing will be soldier flies. Once your bin has soldier flies, it can be difficult to say goodbye to them. Your best tactic is to simply allow them to grow out of the larval stage (which they do quickly) and fly off. If you really can't stand them, you'll have to harvest the worms and get rid of all your vermicompost material (put it in an outdoor compost pile, or bury it in the garden). Then put your worms back into fresh bedding.

Maggots
Maggots are good composters and will not harm your worm bin.

Flat Worms & Land Planarians


Land Planarians, also called Flatworms, are iridescent slimy worms with a hammer or disk shaped head. They eat slugs, each other, and are voracious predators of earthworms. Much like slugs, they hide in dark, cool, moist areas during the day and require high humidity to survive. They are rare in rural sites. Feeding and movement occur at night.


Land Planarians are extremely destructive to earthworm populations and need to be removed and destroyed upon sight. They can survive desiccation only if water loss does not exceed 45 percent of their body weight. They are thought to primarily be distributed by tropical plants. Planarians are a predator that you will want to remove and destroy every time you see one. Spray with orange oil or bleach, or collect to dry out in hot sun.

Land Planarian
Land planarians should be removed from your worm bin immediately.

Jack, ALH, Thies, J and Drinkwater, L (2012) "Selected Invertebrates of the Soil Food Web" [video] Cornell University eCommons, Collection: Cornell Waste Management Institute,
URL: http://hdl.handle.net/1813/28634


34 Responses to What’s In My Worm Bin

  1. Sara Cochran says:

    My worm bin was over run with ants last summer. I scoured the internet and found an effective method. Set the worm bin on bricks or posts of some sort and then set the worm bin and posts in one large container or water.. or four separate ones for the four posts. Either way you are preventing more ants from getting in and those that try to get out drown. Since the compost was almost done they had very little to eat and eventually after keeping the worm bin in this set up the ants all died off and i was ready to harvest compost. If you keep a worm bin outside and aren’t good at keeping it wet, have a large ant problem (like me)..etc. . you may want to keep it in this sort of set up.

    To help with the fruit flies inside/ around worm bins I have found that using an old small vase with a little less than an inch of apple cider vinegar and a squirt of dish soap in it and a paper funnel inserted and left a inch or less above the liquid. The vinegar attracts them, the paper funnel keeps them from being able to fly back out (they aren’t great at flying back up the tube) and the soap when they touch it will coat them and their wings.. so no more flying for the fruit fly.

    I wanted to share because these methods worked wonders for me. I live in Southern Mississippi if that helps anyone.

  2. kate says:

    Sara! Thank you for your awesome comment and tips on handling ants and fruit flies! Yes, standing the legs of the bin in water for ants and creating a vinegar/dish soap trap for fruit flies both work, and are some of our tried and true methods up here in NW Washington as well.

  3. Nancy O'Brien says:

    THANK YOU for posting soldier fly larvae as I was so baffled by these ugly looking things. They keep crawling out of my bin and walking across the floor to stop in the corners of the room. I will not panic now. I had been picking them up with chopsticks and taking them outside and I will continue doing so.

  4. kate says:

    Nancy – I’m so glad we could help identify the little guys! You’re right, they’re not attractive creatures by any means BUT rest assured they are great composters and the adult soldier flies are not “gross” and “dirty” like normal houseflies, and are completely normal around compost.

  5. Dale Clegg says:

    In the last couple of weeks, my bin has been infested with the maggots and larvae pictured above. I do recall seeing a few black soldier flies around a while back, but none recently. These maggots are chubby little things and voracious eaters that seem to thrive on newspaper. In fact, I was shocked a couple weeks ago that the generous amount of shredded paper which covers the castings and food, then sections of papers I use to cover the shredded paper was nearly gone and these maggots were everywhere.

    Not taking the time to find out what they were, I took all the paper out and they seemingly disappeared. So I added paper again and they are back with a vengeance.

    I’m hoping this is just a passing phase, but if the red wigglers can cohabitate with these guys, it certainly appears that my castings production will increase due to the greater volume of food these guys seem to process in comparison to the worms. Any further advice you might have or links where I might learn more would be appreciated.

  6. kate says:

    Dale – Yep, sounds like you’ve got some very happy Black Soldier Fly larvae in your bin! As stated in the article, they are really interesting and beneficial insects and the only problem they can really cause in a worm bin is that of competing with worms for food. Since you’ve noticed that they enjoy paper so much, adding more of that should help satisfy their voracious appetites. For more information on Black Soldier Flies and composting, please see http://blacksoldierflyblog.com/

  7. Susan says:

    My classroom has a worm bin with tiny white insects/creatures that live on the top layer of newspaper and in the base tray where some of the processed compost falls. They don’t match any of the pictures or descriptions above. Does anyone know what they may be and whether or not they are harmful?

  8. kate says:

    Susan: it sounds like they might be white mites, and you can look above under “mites” for ways to eradicate them. They are not harmful.

  9. Chris says:

    So I have mites are they bad to get inside my house?

    • kate says:

      Hi Chris,

      The mites should stay in the worm bin unless you have other moist decomposing material nearby. They aren’t harmful and I’ve never had a problem with them inside my house!

      Best regards – Kate

  10. Maureen says:

    Greeings!
    I have two vege compost bins…they have been very healthy red worm compost bins…right now, both have a large amount of maggots….should I be worried? I am scared!
    Maureen

    • kate says:

      Maureen – my guess is that they are black soldier fly larvae (described in the article above) which are in fact very beneficial in a worm bin. And the flies that these grubs turn into are not the icky houseflies we are used to. I would keep an eye on the grubs in your bin and try to observe the adults when they emerge to identify them. The only potential problem with maggots in a worm bin is that they can compete for food with your worms. Just make sure you’re feeding enough for both the worms and the maggots, and everyone should be happy.

  11. Katherine says:

    I have an in-ground bin and have started having trouble with cockroaches invading. The bin was there for a year before getting them. I’ve not found anything about them online. Any thoughts? pointers?
    Thanks!
    Katherine

  12. lisa says:

    My in ground worm “bin” (a raised bed, dedicated to worm composting) is over run with what I have determined are cluster fly maggots. I noticed these things a few weeks ago and suddenly one day realized I had very few worms. Then one day my house was FULL (think–Hundreds) of flies. I did research and determined they were cluster flies. (If you get them, do not waste time swatting. Get out your shop vac!) I had the idea that they wanted Out as they were all around the windows. I opened the windows and removed the screens, and voila, out they went. Well, when the flies were in the house I noticed no maggots in the bin and the return of the worms shortly thereafter. Just now I went out and noticed a great new population of worms!! And of maggots. :(

    I just sprayed the yard with nematodes, but ran out before I could finish or get to the worm bin. :( Guess I’ll be heading back to the “nematode store” tomorrow.

  13. Sarah says:

    Hi. I have lots of worms that I think are the land planarians you mention above. But, they are black with a yellow stripe down them?? I found one a month or so ago that I removed, but today I found lots – adults and babies! Help!

  14. Pingback: The Great Late Worm Update | Growing A Greener World

  15. Danelle Karth says:

    This is a great article. I have been running my worm compost under the bed for almost two years now. I had a few mites awhile back and one summer the ants found it, but both of those problems are long gone. Now I have another problem that’s definitely out of hand.

    I noticed a couple of drain flies in the bathroom awhile back and thought nothing of it. That population has gone from a couple to more than a couple and I have been working on getting them out of the shower drain. What I didn’t know was that they were taking over my worm bin which after researching their natural habitats in the wild (outside of drains) isn’t that surprising. The moisture in the bin is too high and I am working on getting that under control. I thought if I did that it would take care of the problem, but I came across someone else who had drain flies in their bin and they made it sound like that didn’t help.

    Any suggestions? I really don’t want to get rid of the bin and the worms themselves look great with boat loads of eggs, especially for the cooler weather. Thanks for any help that you might be able to offer.

  16. Julie says:

    Are creepy crawlies more or less common with an indoor bin as compared to an outdoor bin?

    I would assume that some are obviously more common with an outside bin, but I’m concerned about setting up an indoor bin and introducing flies into the house.

  17. Beckie says:

    I’ve only had my worm composted bin for 2 months. I’ve noticed hundreds of 1/2 inch long white elliptical casings (?) floating in the leachate. They have no appendages and are immobile. They look like large rice kernals. Do you know what they might be? And are they harmful?

    • kate says:

      Beckie – It sounds like those might be cocoons of some sort. Can you discern if they have a hole in them anywhere where an insect could have emerged? As long as they’re not alive it sounds like they shouldn’t be harmful. I’d just keep an eye on them to see if anything hatches, and if so, you can describe the creature to me or google search for it to find out what it could be.

  18. Pam says:

    Hi, I have been worm composting for a couple of years now, but a first for me yesterday – tiny little black bugs all around the bin on the floor, and climbing up the walls. Tiny, black and rather hard shelled, . About the size of a fruit fly,but dark shiny black, and not a flying bug. Anyone know what kind of bug these are, and if they are harmful to our home or worms? thanks for any help. Pam

  19. Jeff says:

    Pam, the tiny black bugs sound like Flea Beetles. They love asian greens. Just a thought.

  20. Linda Robish says:

    Please help! My house is being overrun by flies!
    I’m relatively new to vermicompositing; this is only my second winter. The first winter I kept the composter in my basement and everything went fine. But recently I found dozens of black maggots. I removed and destroyed as many as I could. Then I began seeing a few flies. They look like house flies, but they’re smaller and not as agile. (I know what fruit flies look like, and they’re not fruit flies.) I’ve also found a few that are much longer; queens? My basement is now full of these little guys and they’re starting to spread out throughout my house! For the last couple of days I’ve been vacuuming them up several times a day and squirting bug killer into the vacuum hose afterward so they won’t fly back out. I’m so grossed out that I haven’t even opened the composter; I’m afraid of what I might find!
    Recently I took a big batch of food scraps and cooked them up (to speed up their decomposition, I thought). I refrigerated my “worm chow,” and once it was cool, I added some expired foods from my pantry, and then fed the concotion to the worms. This is the only thing I’ve done differently.
    Please help!

    • kate says:

      Linda, take a look at these websites and see if you can identify the flies in your home. Note the color differences and differences in body anatomy.

      http://en.wikipedia.org/wiki/Black_soldier_fly
      http://en.wikipedia.org/wiki/Housefly

      To get rid of flies you have to be persistent. If you have house flies that’s the biggest problem. Remove any larvae and cover the top tray with some type of breathable cloth to prevent mature flies from laying eggs in the compost. Usually house flies don’t bother the composter because it doesn’t contain the type of food they like to eat.

      • Linda Robish says:

        Hi Kate,
        I think I may have had a few (maybe a half dozen) of the soldier fly. All but one was dead on the window sill. My real problem is more similar to the house fly. Their body type and wing shape is like the house fly, but they don’t have the big red eyes. They’re maybe half the size of the houseflies we get here in VA, if that. Unlike house flies, though, they seem to spend more time sitting on surfaces than they do flying around. If I disturb them they fly around, but not as quickly as house flies do. They’re very easy to vacuum up or squish with a tissue because they don’t startle like house flies do; often they just sit there. I keep vacuuming up or squishing the ones I find, but they just keep coming! They’re even in the bottom (drip) tray of the composter. We had warm weather here so I put the composter outside for a couple days and agitated it periodically so they would fly off, but I had to bring it back in, and I have more flies! There have been dozens, if not hundreds of them all together.

  21. nate says:

    hi

    i just set up my red worm bed and notice thousands of red mites!! how do i get rid of them without hurting the new worms

  22. gretchen says:

    How can i get rid of worms, *inside the house* and whats causing them??? I already sprayed the house with sprays from LOWS, no help what so ever! Any advice is greatly appreciated, I have a dog, and cat, both are wormed monthly. Again any advice is greatly appreciated!! Take care!!

    • kate says:

      Hi Gretchen, I’m not sure what kind of worms you’re talking about. Do you mean your composting worms are getting out of the bin and are in your house? They usually die pretty quickly if they exit the Worm Factory.