Bugs! Creepy Crawlies! What’s in my Worm Bin?
In addition to the millions of micro-organisms 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.
PotwormsPotworms 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.
EarwigsEarwigs 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.
BeetlesThe 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.
SpringtailsSpringtails 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.
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)
MitesMites 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.
Mites can compete with the worms for available food if the population spirals too high. High mite populations usually result from:
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.
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.
CentipedesCentipedes 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.
MillipedesMillipedes 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.
Sow Bugs & Pill BugsSow 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.
Pill bugs, or “roly polly bugs” look similar to sow bugs but roll up in a ball when disturbed.
Slugs & SnailsSlugs 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.
AntsAnts 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.
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 FliesExcess 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.
Soldier FliesSoldier 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.
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 LarvaeThe 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.
Flat Worms & Land PlanariansLand 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.
Jack, ALH, Thies, J and Drinkwater, L (2012) “Selected Invertebrates of the Soil Food Web” Cornell University eCommons, Collection: Cornell Waste Management Institute,