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Critters in the Compost

Excerpt from The Complete Compost Gardening Guide by Barbara Peasant & Deborah L. Martin, 2008:

Imagine a huge crowd of hungry people of such different nationalities that they can barely converse about water, much less food. Then, all of a sudden, within various sectors of the crowd, tables laden with food appear – corn tortillas with beans in one place, curried stew in another, and rice scented with ginger and sesame right in the middle. It would be chaos of the highest order as people push and scramble to get what they recognize as food before it runs out.

Something similar happens each time you add material to your kitchen compost. A huge, diversified community of life forms occupy the compost, each with an appetite for a certain small link in the food chain that connects, say, a composting potato peeling first to mold (fungi) and slime (bacteria), later to earthworms, and eventually to a new plant root. The plant root enters the scene eager to take up nutrients left behind in the now shriveled, barely recognizable potato peeling, so it enlists the help of other compost-borne fungi that have been hanging around waiting for what they consider a great meal – steady helpings of nutritious root exudates that the plant pushes to the surface of its root tips. At the last minute, just as the potato peeling turns to humus (finished compost), a root-fungi relationship forms to give the plant roots and the fungi exactly what each needs.

This drama requires a huge cast, made possible by the incredible diversity of ingredients that are fed to the kitchen compost. From fall to spring, the bulk of this activity is quietly carried on by fungi and bacteria, but in warm weather, these microorganisms are often joined by insects attracted by the gases given off by fermenting fruit. Wasps and bees stop in for nips of compost “wine” if it’s available, and at night crickets may use kitchen compost as a place to court and gorge at the same time. Take the time to look at these insects before dismissing them as pesky flies (some are flies, of course).

Drawing by Daniel Dindal from Ecology of Compost: A Public Involvement Project, 1971

Any properly-managed composting activity is teeming with life. This is true of any hot or cold compost pile, sheet mulch, worm bin, bokashi bucket, or a compost pit or trench. The workhorses of this process – bacteria, fungi, and actinomycetes – are invisible to the naked eye. But because these microorganisms thrive in the compost, other creatures that consume them also populate this environment. This ecosystem has become known as the compost food web.

It is the interaction within this community of organisms that turns living and once-living material into the black gold known as finished compost. This happens naturally on a moist forest floor (aerobic) or in a peat bog (anaerobic). When humans get involved in managing this process, it’s called ... composting.

While we should recognize that all of the consumers pictured above are vital components in the process. It may be difficult for some home composters to accept their presence so close to homes, hands, and garden, yet these creatures are as important to maintaining the compost ecosystem as the bacteria and fungi we have come to accept as key elements in composting. However, we don’t necessarily need to let certain organisms proliferate and cause a nuisance.

If you are intent on avoiding insects and similar critters, you can compost in a closed system such as bucket composting with Bokashi.  You can also bury your organics directly in the soil 12 to 18 inches deep (i.e., pit/trench composting).

However, critters in the bin can be beneficial, with some exceptions.  Learn more about them below.

Maggots and Flies

A common complaint from home composters is the presence of maggots, which are the larvae stage of flies. There are several types of maggots, and some are even beneficial to the compost. Common house fly larvae,
however, are not beneficial and are known to carry diseases harmful to humans. On the other hand, soldier fly larvae are the composter’s friend. Their presence helps to control the breeding potential of houseflies, and they are avid consumers of decaying material.

Recognizing the difference, and preventing/controlling house flies while allowing soldier flies to proliferate is probably beyond the degree of involvement that the average home composter wants in the composting process. Flies need exposed food on which to lay their eggs; plus, they are not burrowers. So, to prevent flies, when adding “food” to the compost pile or bin, top it off with a couple of inches of carbon-rich material (such as dry leaves), as well as a tarp or other cover. If the maggots are already present, turn the pile so the material on the edges where the eggs and maggots are ends up in the middle. For the worm bin, the food should be buried in the existing bedding or covered by adding more damp bedding material, along with a secure lid.


Soldier Fly Larvae

Black Soldier Fly, CC BY-SA 4.0


One of the most visible critters in the compost is the grub, the larvae stage of various beetles (often the June beetle).  Don’t be alarmed, because they are good for the compost.  They are present in moist areas where they help aerate and loosen compacted parts of compost materials and break down organic matter as they feed. Their presence is a good indicator that the composting process is not finished because they are still breaking down organic matter. The grubs will die off as the food source in the compost is consumed.

If you do use compost before the grubs disappear (for example to use as an autumn mulch), screen out any live grubs as they might be a problem for plants in garden soil. 

Sifted out grubs (and even maggots) may be euthanized and their dead carcasses may be added back to the unfinished compost pile.

Or, if you happen to have chickens, they will go crazy for the grubs.  Turn the chickens loose on the compost; perhaps spread it out a bit.  It's likely that within half an hour your grubs will have disappeared. You can also pick live grubs out of the pile and place somewhere to feed birds.

Dealing with grubs is one of those chores that we composters have to do. The end result is worth the effort.


If the presence of grubs is just too onerous, they can be controlled with earth-friendly nematodes or by adding carbon-rich material, since the grubs live on green material.


June Beetle Grub


Grubs of Various Kinds

Sow Bugs and Pill Bugs

Since the compost pile/bin is a moist environment, other visible, prolific creatures are the sow bugs, or wood lice. Also related are pill bugs, which roll up; hence the nickname “rolly-pollies.” These isopods are actually crustaceans, related to crabs and lobsters, that have adapted to living completely on land. They are completely harmless, but perform a valuable service in the compost as first level consumers of vegetation, leaf litter, and decaying animal matter.

Sow Bugs and Pill Bugs

Used under Creative Commons Attribution-Share Alike 2.0 License.


Many, maybe even most, people are repulsed by cockroaches. Knowing they are beneficial in the decomposition process does little to diminish the “yuck factor” when most folks encounter cockroaches. They live in compost because it’s an abundant food and moisture source. Unfortunately, by adding too many nitrogen-based materials, such as decaying meat, grease, and dairy, to the compost, it will start to smell. This could easily activate a cockroach problem. If accepting their presence is not an option, cockroaches can be removed with diatomaceous earth, although this will likely have the unfortunate effect of killing other beneficial bugs. Heating up the compost with appropriate C:N ratio organics and moisture content will make a compost pile uninviting for cockroaches and many other creatures. Ensuring the compost bin is sealed, except for the air holes, which should be screened, will keep them out. Also, if the compost pile is exposed, chickens are a useful form of cockroach control.  If you are worried that roaches will move from the compost bin into your home, you can keep the bin as far as possible from your house.  However, there is little evidence that cockroaches move from the bin to the home.  They are quite happy in the bin.

Red Worms

If you are lucky, red worms will show up in your compost.  These critters are highly beneficial. Their excretions are a valued "manure" and will enrich your compost enormously. 


Photo by Wynette Richards


Red Worms

Photo by Tom Nichols

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