What Do Roly Polies Eat? – Solving a Mystery in the Soil

Every gardener encounters roly polies, but few of us truly understand them. What are these strange creatures? Although they look like insects at first glance, roly polies are actually crustaceans. In fact, they are the only such animals to live their entire lives on land, but they are only able to survive in dark, moist environments.


Although quite common in the United States today, many gardeners see them as an annoyance. If these grey-colored creatures are pests, though, what do roly polies eat? As decomposers, they specifically feed on decayed matter and process metals. Roly polies thus play a key role in your garden by building and maintaining the soil.

What Is a Roly Poly?

Roly polies or Armadillidium vulgare are terrestrial isopods in the class Crustacea that are also known as pillbugs. In general, they range from ¼ to ½ inch in length and have oval, convex bodies.

As members of Arthropoda, pillbugs are joint-legged with seven pairs of legs, a tough exoskeleton, and a segmented body.

They are called roly polies because they can roll into a tight ball for protection. This distinguishes them from the related sowbug or Porcellio scaber, who also have tail-like appendages on their rear. Pillbugs are also unique because they can absorb water through their anus and recycled copper through their feces.

Many of the USA’s twelve species are invasive, having immigrated from Europe with the timber industry. They require moist environments like coastal habitats and wetlands, as seen in this video.

Roly polies occasionally wind up indoors, but, unlike other pests, they do not transmit disease, bite or sting, or infest wood, food, or textiles.

What Do Roly Polies Eat?

Pillbugs feed on decaying organic matter. As scavengers and decomposers, these crustaceans thrive under mulch, compost, boards, and stones.

They are nocturnal but may travel long distances at night. Although they are susceptible to dehydration, they can lose a considerable proportion of body water and re-absorb it from the atmosphere.

Much like earthworms, snails, and other decomposers, roly polies rejuvenate soil by recycling organic matter. In particular, they break down nitrates, phosphates, and other nutrients so that plants can easily absorb them. When many amass, pillbugs may feed on seedlings, roots, leaves, or low-lying fruits, as detailed in this video.

Roly polies can become an annoyance when they come indoors or eat plants. This usually occurs in summer, as they reproduce in large numbers. Pillbugs will invade high-humidity areas like damp basements through thresholds, sliding door bases, or expansion joints. However, these creatures cannot damage household structures.

How Do They Support the Soil?

Decomposers in general are essential for gardening and homesteading alike. Roly polies specifically serve as the first step for returning organic matter to the soil.

After these crustaceans have processed decayed matter, fungi, protozoans, and bacteria further break it down to help topsoil develop more quickly.

Pillbugs are especially key for soil with high levels of heavy metals. Due to a high tolerance for toxic metal ions, they can consume and crystallize contaminants as midgut deposits that are excreted. Although roly polies do not urinate, these decomposers also convert wastes high in ammonia into urea and pass that gas through their exoskeletons.

In so doing, they help restore contaminated soil by speeding the recovery and formation of topsoil. This in turn helps plants more quickly establish their roots in more stable soil. Roly polies thus prevent these contaminants from leaching into ground water or creating toxic dust.

You may even want to establish a roly poly culture, as shown in this video.

How Can You Control Them?

When these otherwise important crustaceans amass in too large a number, their presence can be a nuisance. However, their need for moisture means that roly polies generally cannot survive indoors for more than a few days. The most effective approach is to eliminate the conditions that attracted these creatures in the first place.

  • Start by removing any roly polies indoors with a broom or vacuum.
  • Then, reduce humidity indoors by improving ventilation and air conditioning units.
  • Find and remove piles of leaves, mulch, stones, and boards near the foundation.
  • In Gardens, use coarse mulch to keep water from accumulating around plants.
  • Fix and maintain gutters, down spouts, faucets, pipes, and outdoor AC units.
  • Ensure proper drainage with tiles, drains, or sloping, as well.
  • Seal entry points at thresholds, windows, joints, and interior basement walls.

If these methods fail, or when you have a large infestation, consider certain insecticides. These include abrasive diatomaceous earth as a barrier around plants, insect killer granules to repel them from your foundation, and botanicals like neem oil to treat problem areas.

This video walks you through the various options available for effectively repelling roly polies. Use chemicals sparingly, and focus on preventing moist conditions.

The Mystery of Roly Polies

Roly polies seem like a standard insect, but they play a key role in consuming toxins and building topsoil. When issues arise, the best approach is to remove the moisture and allow roly polies to do their work. However, you can use the preventative treatments above to deal with larger invasions, in particular.

Comment below if you have any questions about these mysterious yet important crustacean creatures.

About the Author Laura Bennett

Hello, I’m Laura Bennett. I love nature especially when it comes to flowers and different kinds of plants. I started a very small garden behind my house and I named it Humid Garden. So, I created this blog to provide aspiring and inspiring thoughts about gardening for gardeners and anyone who has the intention of keeping a garden.

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