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.
Potworms

Potworms are common in worm bins and enjoy slightly acidic conditions.
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 can be identified by their pincers on the back of their abdomens.
Beetles

The rove beetle is the most common beetle in worm bins.
Beetles are not harmful in the worm composter.
Springtails

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 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:
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

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

A millipede has a round body and has two pairs of legs per body segment.
Sow Bugs & Pill Bugs

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

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.
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.
Ants

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

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

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

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

Land planarians should be removed from your worm bin immediately.
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,
URL: http://hdl.handle.net/1813/28634