Common Pests

While working with your worm composter you may encounter some other critters besides your worms. Here we have a few of the more common invertebrates that may show up in or around your worm bins



Ants feed on fungi, seeds, sweets, scraps, other insects and sometimes other ants. Compost provides some of these foods and it also provides shelter for nests and hills. Ants may benefit the compost heap by moving minerals especially phosphorus and potassium around by bringing fungi and other organisms into their nests. The presence of ants is an indication of dry bedding. Moisten the bedding a bit and most ants will find some place else to live. If your bin has legs, place the legs in a can of water that has had a drop of dish soap placed in it to reduce the surface tension of the water so the ants can't walk across the water.



Centipedes are fast moving predators found mostly in the top few inches of the compost heap. They have formidable claws behind their head which possess poison glands that paralyze small red worms, insect larvae, newly hatched earthworms, and arthropods - mainly insects and spiders. Remove carefully because they can harm you.


Cluster Fly
Cluster Fly

Cluster Flies ( Pollenia rudis ) Sometimes called "attic flies", usually appear in late fall or early winter and again on warm, sunny days in early spring. They buzz around the home and gather in groups at windows. The cluster fly is a little larger than the common housefly and moves more slowly. It can be recognized by the short, golden colored hairs on its thorax, the part of the insect that the wings are attached to. The larvae, or maggots of cluster flies develop as parasites in the bodies of earthworms. The adult flies emerge in late summer and early autumn and seek protected places to spend the winter.



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 other insects, worms, snails, slugs and other small animals. Rove beetles are slender, elongate beetles with wing covers (elytra) that are much shorter than the abdomen; over half of the top surface of the abdomen is exposed. Most rove beetles are black or brown. One species has gray markings on the wings and abdomen. Most rove beetles are medium sized beetles, a few species are up to 1 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. In New Zealand these insects, commonly called the Devil's Coach-horse, predate upon flatworms and slugs. They can be very numerous in compost and vermicompost.


Fruit Fly

A Fruit Fly is about one third the size of the housefly. Adults have red eyes and yellow-brown bodies. Life cycle from egg to adult is approximately 10 days. Eggs are laid near or on top of fermenting materials, such as decaying fruit and vegetable matter. They are attracted to any area where moisture has accumulated. Flies are natural organisms in any decomposition system. Always keep 3 to 4 inches of shredded moist newspaper on top of your worm bin to make it difficult for the female flies to lay eggs in the food waste. To prevent fruit fly infestations you can freeze or microwave your food waste prior to placing in your bin. This destroys eggs and larvae that live on the peels. Allow the material to reach room temperature prior to feeding to worms. To reduce existing fruit fly populations you can use a trap or find some beneficial nematodes from your local garden center and add them to the bin.



Pot Worms are very small, little white worms that can reach densities of 250,000 individuals per square meter. The highest populations are found in acid soils. They feed on bacteria and fungi. They eat dead organic matter and small feces. They ingest small mineral particles and probably play an important role in mixing organic matter into the mineral soil. They have no enzymes for digesting complex polysaccharides and thus do not digest the organic matter they ingest. They are good for your compost system and harmless to you, your worms and plants. Enchytraeids are sometimes raised as fish food.


Information courtesy of Dorothy Benoy at