Sowbugs in New Hampshire — ID, Pillbug Lookalike & Control
Also called woodlouse · slater
The sowbug is the pillbug's close cousin — also a land crustacean (isopod), not an insect — but with two key differences: it cannot roll into a ball, and it has two short pointed 'tails' at its rear end. Harmless, moisture-dependent, and unable to survive dry indoor conditions, it is a perimeter-moisture indicator, not an infestation.
- What it is
- Crustacean (isopod), not an insect
- University of Kentucky Entomology
- Key tell
- Cannot roll into a ball; two short rear tail-points
- Missouri Dept. of Conservation
- Size
- ~¼–½ in (to ~17–19 mm)
- University of Kentucky Entomology
- Legs
- Seven pairs (14 legs)
- University of Kentucky Entomology
- Dangerous?
- No — beneficial decomposer
- University of Kentucky Entomology
- Indoor survival
- Dies — dries out without moisture
- University of Kentucky Entomology
The pillbug's cousin that can't roll
The sowbug is the pillbug's close cousin — also a land crustacean (isopod, not an insect) — but with two immediate distinguishing features: it cannot roll into a ball when disturbed, and it has two small pointed 'tails' (uropods) projecting from its rear end. Both facts matter for fast field ID: if the gray bug under the flowerpot stays flat and scatters rather than curling into a sphere, you have a sowbug. Like the pillbug, it is completely harmless — no biting, no stinging, no disease — and a beneficial decomposer of decaying plant matter in the garden.
The damp story is identical to the pillbug's: it lives in damp soil, mulch, and leaf litter and wanders indoors from the perimeter when conditions are wet. Indoors it cannot survive — it dries out and dies — so it is a humidity symptom, not a true infestation. The durable fix is drying the foundation perimeter: pull mulch and leaf litter back at least six inches from the wall, fix grading and drainage so water flows away from the house, and seal door sweeps and foundation gaps.
How to identify a sowbug
Two features immediately separate a sowbug from the closely related pillbug: it cannot roll into a ball, and it has two short pointed rear appendages (uropods). Secondary confirms are the flatter body profile, the small lateral plate flares along the sides, and seven pairs of legs (confirming it is not an insect).
Sowbug
- Scientific name
- Porcellio scaber / Oniscus asellus
- Family
- Porcellionidae / Oniscidae
- Size
- ~¼–½ in (to ~17–19 mm)
- Coloration
- Gray to brownish-gray, sometimes slightly mottled; flatter profile than a pillbug
- Habitat
- Under logs, rocks, leaf litter, mulch, and damp soil; gardens and foundation perimeters
- Active season
- Spring through fall, nocturnal
- Diet
- Decaying plant matter (detritivore); beneficial decomposer
- Reproduction
- Females carry eggs and young in a brood pouch (marsupium)
- Lifespan
- ~2–3 years
Introduced from Europe (Old World); now cosmopolitan worldwide. Common throughout New Hampshire.
The tells — key ID features
- Cannot roll into a ball when disturbed — the defining distinction from the pillbug.
- Two short pointed 'tails' (uropods) projecting from the rear end — visible on close inspection.
- Flatter body profile than a pillbug, with small plate flares along the sides.
- Seven pairs of legs (14 total) — confirming it is a crustacean, not an insect.
- Gray to brownish-gray, ~¼–½ inch.
- Always in damp spots — under mulch, pots, leaf litter, or near a damp foundation threshold.
Size, to scale
~¼–½ in (to ~17–19 mm)
About the same size as a pillbug — roughly a pencil eraser — but flatter and it stays flat when disturbed.
Pillbug
How to tell — A pillbug rolls into a tight, complete sphere when disturbed and has no rear tail-points. A sowbug stays flat and has two short pointed uropods at the rear. The roll test settles it instantly.
Woodlouse (general)
How to tell — 'Woodlouse' is the umbrella name for both sowbugs and pillbugs. If it cannot roll and has rear tails, it is specifically a sowbug.
Signs of a problem
Sowbugs, like pillbugs, signal their presence by location rather than damage. Look for these patterns.
Flat gray bugs that scatter without rolling when you lift mulch, pots, or boards
What it means — Sowbug harborage in damp perimeter material — the can't-roll behavior is the instant tell.
Sowbugs found indoors near damp basement walls, doorways, or crawl-space entries
What it means — Moisture entry from the damp perimeter — they wandered in through gaps and cannot survive indoors.
Many sowbugs in compost or garden beds
What it means — Normal, beneficial decomposition in healthy moist soil — not a problem in the garden.
Dead or dried-out sowbugs found inside
What it means — They entered through a perimeter gap but could not survive dry indoor conditions — confirms moisture entry.
The real risks, calibrated
Sowbugs are harmless to people, pets, and home structures. Their only significance indoors is as a moisture indicator.
Bite, sting, or disease
Low riskOnset: N/A
Sowbugs do not bite, sting, or carry disease. No human health risk has been documented.
Minor seedling or soft-fruit feeding
Low riskOnset: Outdoors in growing season
Occasional minor feeding on very tender seedlings or soft fruit touching the soil; rarely significant.
Indoor survival
Low riskOnset: Upon entering a dry interior
Sowbugs dry out and die indoors — they cannot breed or establish an indoor infestation.
Foundation-moisture indicator
Low riskOnset: Ongoing presence at perimeter
A sowbug population at the foundation signals persistently damp conditions worth addressing.
DIY — what works, what backfires
The fix for sowbugs is the same as for pillbugs: dry the foundation perimeter. Interior spraying is unnecessary — they cannot survive inside anyway.
What actually works
- Pull mulch, leaf litter, and ground cover back at least 6 inches from the foundation wall.
- Fix grading and drainage so water slopes away from the house rather than pooling against the foundation.
- Seal door sweeps, foundation cracks, and crawl-space gaps — these are the entry routes from the perimeter.
- Sweep or vacuum any indoor sowbugs; they cannot survive without exterior moisture.
- Reduce damp harborage under porches, decks, and garden structures near the house.
What backfires
- Don't treat a sowbug indoors as an infestation — it cannot breed or survive without perimeter moisture.
- Don't pile damp mulch, leaf litter, or firewood against the house foundation.
- Don't spray indoors — the perimeter moisture is the issue, not the sowbug inside.
Sowbugs in New Hampshire gardens and homes
Across Manchester, Nashua, Concord, and southern NH, sowbugs are common in gardens and around damp, mulched or leaf-littered foundations — especially in shaded areas that stay wet. They wander indoors during wet periods or when perimeter moisture is persistently high, entering through door sweeps, foundation cracks, and basement windows. Like pillbugs, they cannot survive dry indoor conditions, so dead ones found inside are a clue that moisture is entering at the perimeter.
Peak season
Spring through fall, most active in warm wet weather
You might actually have
- Pillbugs (close cousin that rolls into a ball — the rolling test tells them apart)
- Woodlice (umbrella term covering sowbugs, pillbugs, and related isopods)
- Springtails (also a moisture indicator — tiny hopping specks)
We serve these communities
- NH-licensed applicator · #782664
- Same-day service
- Family-owned since 2017
Service Area Map
Southern New Hampshire
When to call a pro for sowbugs
If sowbugs are consistently entering the home despite perimeter moisture management, a licensed technician can address foundation moisture and exclusion in combination — and confirm whether harder-to-fix drainage or seepage issues are the underlying driver.
When to call a pro
- Persistent indoor sightings despite removing damp harborage and fixing drainage.
- Suspecting foundation seepage or drainage issues beyond standard grading.
- Large seasonal influxes during wet spring or fall weather.
Keep mulch off the foundation
Maintain at least 6 inches of clearance between mulch, leaf litter, and the foundation wall year-round — this is the most impactful sowbug prevention step.
Fix drainage and grading
NH's clay-heavy soils can trap water against foundations. Re-grade to slope water away and extend downspouts to discharge water several feet from the house.
Seal entry gaps
Replace worn door sweeps and seal foundation cracks and crawl-space vents. Sowbugs enter through very small gaps, so thorough sealing matters.
Not sure it's a sowbug?
A licensed NH technician can confirm the species and tell you honestly whether it's a DIY fix or a job for a pro — free inspection, same-day service across Southern New Hampshire.
Frequently asked questions
Sources(4)
- [1]University of Kentucky Entomology — Sowbugs and Pillbugs
crustacean classification, seven leg pairs, gill breathing, indoor survival, no health risk
extensionverified 2026-06-30 - [2]Missouri Dept. of Conservation — Pillbugs and Sowbugs
cannot roll, two rear tail-points, genera Porcellio and Oniscus
govverified 2026-06-30 - [3]UF/IFAS — Pillbug (EENY630)
isopod biology, European introduction, cosmopolitan distribution
extensionverified 2026-06-30 - [4]UNH Cooperative Extension — Insect Identification
NH presence and moisture-first guidance
extensionverified 2026-06-30
Written & reviewed by
VerifiedDaniel Brady
NH-Licensed Pesticide Applicator · License #782664 (NHDAMF, RSA 430)
Daniel Brady is the New Hampshire–licensed applicator behind Anchor Pest Services, a family-owned pest control company serving the Manchester area since 2017.
Last updated 2026-06-30
New Hampshire pest control
Dealing with sowbugs in your home?
Anchor Pest Services identifies and handles sowbug problems across southern and central New Hampshire. Family-owned since 2017, NH license #782664.
- NH-licensed applicators (#782664)
- Same-day service · free inspection
- Family-owned since 2017