Millipede House Invasion

📐 FIELD GUIDE ILLUSTRATION

Odorous House Ant (Tapinoma sessile) identification illustration with labeled anatomical features — PestControlBasics.com

Original illustration by PestControlBasics.com. Use anatomical labels above to confirm your identification.

📐 FIELD GUIDE ILLUSTRATION

House Fly (Musca domestica) identification illustration with labeled anatomical features — PestControlBasics.com

Original illustration by PestControlBasics.com. Use anatomical labels above to confirm your identification.

🔬

PestControlBasics Editorial Team

Reviewed by Derek Giordano · Updated 2026

🔍 Identification

Three species commonly invade homes:

Flat-backed Millipede (Polydesmida): 20-50mm; flattened body with lateral keels; produces defensive cyanide compounds — don't crush near face. Most common.

Greenhouse Millipede (Oxidus gracilis): 15-22mm; slender; introduced; associated with greenhouses and moisture near structures. Light brown.

Rusty Millipede (Trigoniulus corallinus): 15-20mm; bright rust-red; common in the Southeast US and Hawaii.

🧬 Biology & Behavior

All millipedes are detritivores — they eat decaying organic material. All require high moisture. All can be found outdoors in millions, which concentrates them near structure foundations during dry periods or rain. They can't breed indoors — all individuals entering structures die within 24-48 hours without moisture.

⚠️ Damage & Health Risk

Nuisance only; flat-backed millipede chemical secretions can cause skin irritation; no structural damage; no disease.

🔧 DIY Treatment

Address moisture: remove mulch from foundation contact; fix drainage; reduce irrigation against foundation. Apply bifenthrin perimeter spray. Install door sweeps. CimeXa dust in crawl space and basement gaps. Indoor individuals die naturally — vacuum or sweep rather than spray.

👷 When to Call a Pro

Rarely warranted alone. Moisture control is the lasting solution.

❓ FAQ

Why do I get thousands of millipedes every spring?

Spring millipede invasions happen when outdoor soil becomes waterlogged (from snowmelt or spring rain) and millions of soil millipedes simultaneously surface and move toward higher, drier ground — which often means your foundation and walls. Improving foundation drainage dramatically reduces this annual cycle.

Are millipede secretions dangerous?

Flat-backed millipedes (Polydesmida) produce benzoquinones and hydrogen cyanide as defensive secretions. These can cause skin discoloration and mild irritation if you crush them against your skin. Their secretions are harmless in normal encounters but wash hands after handling.

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 🐛 House-Invading Millipede Species

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.

🐛 House-Invading Millipede Species