Pillbugs, often called "roly-polies," and sowbugs, sometimes referred to as "woodlice," are common outdoor crustaceans that are frequently mistaken for insects. Understanding their diet and habitat is crucial for managing their presence in gardens and homes. This article delves into the specifics of their feeding habits, preferred environments, and strategies for controlling their populations.
Identifying Pillbugs and Sowbugs
Pillbugs (family Armadillididae) and sowbugs (family Porcellionidae) are not insects or true bugs; they are soil-dwelling crustaceans in the order Isopoda, known as isopods. Adult pillbugs and sowbugs are distinguished from insects and other many-legged creatures by having seven pairs of legs.
Adult pillbugs and sowbugs have a small head and six small abdominal segments. They also have seven relatively large thoracic segments, each having a pair of legs. Pillbugs and sowbugs have a hard, shell-like covering made up of a series of segmented plates, a significant difference from the body segments of insects. The body of pillbugs and sowbugs are oblong to oval-shaped with an arched or half-domed (convex) back. The top of sowbugs is more flattened in comparison with pillbugs. The young (immatures) are pale yellow to whitish and about 1/12 inch long when they emerge from their mother's brood sac.
Males and females can be distinguished by examining their underside. Males have copulatory organs on the front underside of the thorax. When disturbed, pillbugs commonly curl into a ball resembling a pill, hence their common name. Sowbugs cannot roll into a ball and commonly scurry away when disturbed. Pillbugs have a smooth rounded rear end, while sowbugs have distinct appendages protruding from their rear.
Habitat Preferences
Sowbugs and pillbugs thrive in moist environments. Common habitats include:
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- Under mulch
- Compost piles
- Stones
- Flowerpots
- Other damp ground areas
- Damp basements
- First-floor levels
- Garages
These creatures are heavily reliant on ambient humidity to survive. Pill bugs’ rolling into a ball is not only for defense but to retain water. Due to this need for moisture, isopods are largely nocturnal and live in damp spaces. Outdoors, this includes leaf litter, mulch, and under stones or other decorative items. Identifying damp places in and around the home that could harbor isopods is key to successful management.
Pill Bug Diet
Pillbugs and sowbugs feed primarily on decaying plant material and are important decomposers of organic matter. Their diet includes:
- Decaying plant matter
- Rotting vegetation
- Soft decaying plants like grasses and leaves
- Mulch
They occasionally feed on seedlings, new roots, lower leaves, and fruits or vegetables touching the soil. Sowbugs and pillbugs are scavengers and their main source of food is decaying organic matter, but they can feed on live plant material when populations are high and the availability of decaying plant material is small. Pill bugs, sometimes also referred to as roly-pollies, primarily consume plant matter that is either decaying or is already dead and decomposed.
Strange Feeding Habits
Pill bugs do have some rather peculiar feeding habits since they are known to eat their own feces, as well as feces from other animals. Additionally, sometimes pill bugs will feed on decomposing animal flesh.
Life Cycle and Reproduction
Eggs are retained in a brood sac on the underside of females. Eggs hatch about 1 month after being produced, and the young remain in the brood sac for about 2 weeks before they emerge. The young pillbugs and sowbugs molt (shed their covering and grow a newer, larger covering) about every 1 to 2 weeks over a several-month period as they grow into adults. Adults can live for 2 to 5 years.
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Eggs are laid by females and are carried in a pouch beneath the body. Young sowbugs and pillbugs, much like the adults, hatch from the eggs. The young remain in the pouch for up to 2 months after hatching. In about a year, they grow to maturity and breed mainly in the spring.
Managing Pillbug and Sowbug Populations
If pillbugs or sowbugs are a problem, reducing the amount of decaying organic matter on soil and minimizing wetness of the soil surface can help.
Prevention Strategies
Homeowners can prevent future pill bug infestations by eliminating moist sites in and around the home as well as food sources such as vegetable or plant debris.
- Reduce Moisture: The best control to limit indoor entry is to reduce moisture near the foundation. Don’t allow moisture to accumulate near the foundation. Make sure that you have diverted water away with working gutters, downspouts, and splash blocks.
- Clear Debris: Mulch, leaves, and other plant debris need to be cleared because this material attracts sowbugs and pillbugs. Removing leaves, mulch, rotting wood, stones, and flowerpots close to entrances and foundation may greatly reduce unwanted visitors.
- Adjust Irrigation: Reduce the frequency of irrigation to the extent compatible with healthy plant growth. Irrigate early in the day so surfaces are drier by evening.
- Modify Landscaping: Keep compost and mulch back from plants and building foundations. Using raised beds or planting boxes, plastic mulch instead of organic material, and drip or furrow irrigation instead of sprinklers usually keeps pillbugs and sowbugs from becoming serious problems.
- Repot Plants: Repot plants in infested soil.
Protecting Plants
Sowbugs and pillbugs generally do little or no harm to plants. In large numbers, they can feed on plants or small roots if no preferred food source is available.
- Protect Seedlings: Protect young seedlings with paper towel collars, duct tape collars, or waiting until the plants are large enough to transplant.
- Provide Alternative Food: Providing enough decaying organic matter in high-population areas can help prevent live plant damage.
Chemical Control
Indoor insecticide applications are typically of little use as pill bugs and sowbugs will usually die due to lack of moisture indoors. If you find one of these isopods indoors, it is safe to simply pick them up and relocate them outside.
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- Insecticides: Insecticides can be used when all else fails. Always follow the product's label and ensure the product is effective against pillbugs/sowbugs.
- Perimeter Applications: Perimeter applications of pyrethroid products on the foundation of the home in spring or fall can limit isopod entry.
Pill Bug Damage
Although pill bugs may infrequently eat garden or other plants around a home, they rarely do so to the extent that they cause damage. Should a gardener see pill bugs in the garden and suspect them of damaging their plants, while that is possible, it is more likely that it is a slug or some other garden pest doing the damage.
Additional Information
Physical Characteristics
Pillbugs (family Armadilidiidae) and sowbugs (family Porcellionidae) are both oval-shaped, with bodies that are convex above and flat or hollow underneath, and rarely reach more than ¾ inch (19mm) in length. The head and abdomen are small, but the thorax is larger, composing of seven hardened individual, overlapping plates. These isopods also have seven pairs of legs. Sowbugs are distinct in that they have two prominent tail-like appendages (uropods) and cannot roll into a ball. Pill bugs and sowbugs are completely harmless and will not bite or sting.
Nocturnal Behavior
Without high moisture, pillbugs and sowbugs find it almost impossible to survive indoors.
Isopods as Pets
Terrestrial isopods have become popular pets. Many native species can be caught around your home and put into terrariums or vivariums to help break down plant matter. In general, it is important to provide a moisture gradient to allow the isopods to self-regulate.