Noticing scores of millipedes congregating in the garden or crawling across basement floors can be disconcerting. But is a high concentration of millipedes problematic or just indicative of environmental factors at play? Understanding what abundant millipede populations signify helps homeowners respond appropriately when they appear.

Millipedes Seek Sheltered Habitats

A key insight into large millipede gatherings is their affinity for cool, moist habitats:

  • As arthropods, millipedes lack waterproofing and easily desiccate without sufficient humidity.
  • Damp basements, mulch beds, and shady lawns suit their moisture needs well when present in large numbers.
  • Young millipedes in particular require dampness for molting since their exoskeletons harden over time.
  • When climate conditions grow too hot or dry outdoors, they migrate into homes seeking cooler, more humid relief.
  • Basements often see the largest congregations aiming to escape summer heat.

Abundant millipedes simply indicate suitable humid microclimates present either indoors or outdoors.

Significance of Major Food Sources

Large millipede gatherings also signify an ample food supply in the vicinity:

  • An abundance of rotting leaves, logs, and organic debris fuels millipede diets, allowing populations to swell.
  • Compost piles and mulch heaps provide buffets that congregate millipedes.
  • Aging, thick layers of natural leaf litter support more millipedes than fresh thin coverings.
  • Supplements like manure, sewage, or kitchen waste also boost numbers.
  • Some species of fungi and mold attract specialized feeders when fruiting prolifically.

The more nutritional resources available, the more millipedes the area can support.

What Seasonal Factors Are At Play?

Time of year often influences millipede population densities based on life cycles:

  • Warm seasons with ample moisture, shelter, and leaf litter facilitate rapid spring and summer breeding.
  • Cool, rainy fall weather prompts mating and egg-laying in preparation for winter dormancy.
  • Hot, arid conditions concentrate millipedes in cooler refuges.
  • Cold winter temperatures force them to retreat deeper into soil.
  • The start of spring rains leads to reemergence and peak food consumption.

Noting local seasonal conditions explains certain population booms.

Have Predators Declined?

An absence of predators hunting millipedes can also allow populations to expand unchecked:

  • Birds, reptiles, amphibians, spiders, and centipedes all help regulate millipede numbers if present.
  • Use of outdoor pesticides may inadvertently reduce predator levels.
  • Removal of stumps, stones, and decaying wood shelter decreases native predators.
  • Invasion of foreign millipede species may lack adapted local predators.
  • Domestic pets discouraged from hunting them no longer help control populations.

With fewer biological checks in place, millipede numbers can grow exponentially.

How Long Have They Been Established?

The duration that millipedes have inhabited an area also influences how abundant they become:

  • Long established populations build gradually over years.
  • Recent colonizers exhibiting rapid growth are still expanding into suitable habitat.
  • One-season swarms may represent a temporary population spike, not a permanent establishment.
  • Preventing chronic infestations requires early intervention.

Noting native species present for decades rather than invasive newcomers provides context.

Do Congregations Cause Damage?

Despite unsettling homeowners, high millipede concentrations rarely inflict damage:

  • Millipedes do not consume living plant matter, only decaying organic debris.
  • They do not structure damage homes beyond minor paper chewing.
  • Millipedes are harmless to humans, pets, and plants directly.
  • At most, dense swarms may kill young seedlings through trampling.
  • Fungus cultivation on humid surfaces may develop.

Monitoring confirms docile behaviors, preventing overreactions to large groupings.

FAQ About Abundant Millipedes

Are a lot of millipedes bad?

Large millipede congregations are primarily just visibly unsettling, not inherently detrimental. They indicate suitable habitat conditions. Monitoring confirms they do not consume living plants or damage structures beyond superficial paper chewing. A live-and-let-live approach is often suitable.

What causes millipedes to come in swarms?

Favorable cool, moist conditions allow millipede populations to boom, especially in autumn. Ample leaf litter and rotting logs provide nutrition to further feed swarms. Reduced predator pressure also enables exponential population growth.

Should I worry about seeing hundreds of millipedes?

Seeing hundreds of millipedes may be disturbing but is often a natural seasonal phenomenon when conditions are ideal for breeding. Document their habits to confirm they remain harmless. Prevent indoor entry points and gently reduce excessive populations as needed through traps and amended habitat.

What should I do if millipedes invade my house?

If swarms do enter homes through cracks in siding and foundations, institute preventative measures. Seal entry routes, set out traps, apply insecticides, and install dehumidifiers to quickly reduce the incursion. Removal and blocking access usually resolves indoor millipede problems.

Why are there suddenly so many millipedes?

Soft rains, ample leaf litter, and warming temperatures often lead to rapid millipede reproduction and congregating. Displaced millipedes may also migrate en masse indoors seeking cooler, humid relief when hot, dry spells hit. Seasonal conditions drive most sudden population surges.

Are millipedes harmful if there are a lot?

High millipede numbers do not make them dangerous, since they remain harmless herbivores. At most, minor seedling damage may occur if rampant populations trample gardens. Mostly they indicate suitable habitat supporting thriving detritivore populations processing organic matter.

Should I call an exterminator for millipedes?

In most cases, simply sealing cracks they use to enter, trapping stragglers, and releasing them outdoors resolves indoor millipede swarms. Serious outdoor infestations damaging plants may require targeted insecticide applications to reduce excessive grouping. But extermination is rarely needed.


Homeowners often react anxiously to the sudden appearance of scores of millipedes on their properties. But close monitoring and research into their behaviors relieves concerns over risks and damage from sizable millipede communities. Abundant millipedes point to ideal conditions facilitating temporary population growth, not dangerous pests requiring eradication. Appreciating their role as essential decomposers encourages peaceful coexistence.

About the author : Shaun W