Soil Millipede & Flat-Backed Millipede

📐 FIELD GUIDE ILLUSTRATION

Millipede and pill bug identification illustration with labeled anatomical features — PestControlBasics.com

Original illustration by PestControlBasics.com. Use the labeled features above to confirm your identification.

🔬

PestControlBasics Editorial Team

Reviewed by Derek Giordano · Updated 2026

🔍 Identification

North American Millipede (Narceus americanus): Large (up to 4 inches); dark with pink-red bands on segments; rolls into a tight coil when disturbed. Found in forests and wooded suburbs.

Flat-Backed Millipede (Polydesmida order): Flattened with prominent lateral keels (flanges); various colors; doesn't roll as tightly. Very common in garden mulch and leaf litter.

House Millipede (Narceus gordanus): Smaller; cylindrical; very common in southeastern US basements and crawl spaces.

🧬 Biology & Behavior

All millipedes: detritivores that feed on decaying plant material. Require moisture to survive — their movement into structures is driven by excessive moisture outdoors (flooding) or attraction to indoor moisture. They cannot establish indoor populations without a sustained moist organic food source.

⚠️ Damage & Health Risk

No biting, no stinging, no structural damage. Some species produce defensive secretions (hydrogen cyanide or benzoquinones) that can cause skin irritation if handled. The flat-backed millipede's keeled defensive secretions can cause chemical burns if rubbed against eyes.

🔧 DIY Treatment

Reduce moisture: fix drainage issues, reduce mulch depth, remove leaf litter from foundation contact. Apply bifenthrin perimeter spray. Exclusion: door sweeps, foundation sealing. Indoor individuals will die within 24-48 hours without moisture.

👷 When to Call a Pro

Rarely warranted alone.

❓ FAQ

Can millipedes hurt you?

Most millipedes are harmless if handled. Some species produce defensive chemical secretions that can cause skin irritation or mild allergic reactions — wash hands after handling. Flat-backed millipedes (Polydesmida) produce benzoquinones that can cause temporary discoloration of skin. None are dangerous.

Do millipedes eat plants?

No — millipedes are decomposers that eat decaying organic matter. They don't eat living plant roots or leaves. If millipedes are found near damaged plants, the plants were already in decline from another cause.

Factor	Details
U.S. Range	All or most U.S. states
Regional Detail	Distribution varies — consult your local extension service for regional prevalence data.

Factor

Details

U.S. Range

All or most U.S. states

Regional Detail

Distribution varies — consult your local extension service for regional prevalence data.

📅 Treatment Timing Guide

Treating at the right time dramatically improves results. Pest control timed to the life cycle uses less product and achieves better long-term control.

Period	Action
Spring	Inspection and perimeter treatment before pest season starts.
Summer	Active monitoring and targeted treatments as needed.
Fall	Preventive treatment before overwintering pests seek entry.

Period

Action

Spring

Inspection and perimeter treatment before pest season starts.

Summer

Active monitoring and targeted treatments as needed.

Fall

Preventive treatment before overwintering pests seek entry.

💰 Professional Treatment Costs

Service Type	DIY Cost	Professional Cost
Initial inspection	Free (self-inspect)	$75–$150 (often credited to treatment)
One-time treatment	$30–$100 in materials	$150–$500
Annual service contract	N/A	$400–$900/year
Severe infestation	Often ineffective alone	$500–$2,500+

Service Type

DIY Cost

Professional Cost

Initial inspection

Free (self-inspect)

$75–$150 (often credited to treatment)

One-time treatment

$30–$100 in materials

$150–$500

Annual service contract

N/A

$400–$900/year

Severe infestation

Often ineffective alone

$500–$2,500+

Prices vary by region, property size, and infestation severity.

❓ Common Questions About 🐛 Soil & Flat-Backed Millipede Guide

How do I confirm I actually have this pest (not something similar)?

The most reliable confirmation is a physical specimen — capture one and compare to reference images on this page. For cryptic pests (bed bugs, termites), look for secondary signs: frass, shed skins, mud tubes, or bites with a specific pattern. When uncertain, a professional inspection is faster than months of misidentification.

Can I treat this myself or do I need a professional?

DIY is effective for small, accessible infestations caught early. Professionals are worth the cost when: the infestation is inside wall voids or structural elements, multiple rooms are affected, you have health-risk pests (hantavirus, venomous species), or DIY has already failed twice.

How long until the infestation is completely gone?

Expect 3–8 weeks for most infestations with proper treatment. Insects with dormant life stages (pupae, eggs) extend the timeline because those stages are impervious to most insecticides. Follow-up treatments at 2 and 4 weeks catch each new cohort as they emerge.

What's the most common mistake people make treating this pest?

Treating only the visible pest population while ignoring the harborage site, entry point, or breeding location. Killing adults provides temporary relief but the population rebuilds from hidden egg cases, pupae, or new arrivals through unaddressed entry points.

🐛 Soil & Flat-Backed Millipede Guide