Camel Crickets and Centipedes in PA Basements: Dry It Out, Seal It Up

Why these four pests show up in the same basements

Camel crickets, house centipedes, silverfish and millipedes look nothing alike, but they want the same things: dark, damp, cool places and something to eat. A lot of homes in our area give them exactly that. Fieldstone and block foundations on older farmhouses and twins let in ground moisture, and houses on wooded lots or near creeks sit in damp soil. Finished basements in newer homes can hide leaks and condensation behind drywall and carpet.

That is why moisture control is the first step for every pest on this page, and treatment on its own rarely holds if the basement stays wet. The US EPA recommends keeping indoor relative humidity below 60 percent, ideally between 30 and 50 percent. A basement that sits at 70 percent in August will keep producing crickets, centipedes and silverfish.

Camel crickets (cave crickets)

Camel crickets, also called cave crickets or spider crickets, are tan to brown, humpbacked and wingless, with very long back legs and antennae. They do not chirp. When startled they jump, often straight toward you, which is most of why people hate them. The greenhouse camel cricket, an introduced species, is common in homes in the eastern US, along with native cave crickets.

They live in damp basements, crawlspaces, garages, window wells and sheds. Outdoors they hide under stones, logs, firewood and deep mulch. North Carolina State Extension notes they can damage fabric and linens stored in boxes during heavy infestations, but they are mostly a nuisance. They generally breed indoors only where it stays dark and moist all the time.

Search interest for camel crickets in the Philadelphia market peaks in November, when cooler weather pushes them toward foundations and into basements. Sticky traps set along walls, behind the water heater and near the sump show where they are coming from and how many there are.

• Run a dehumidifier and fix grading, gutters and downspouts that wet the foundation
• Seal gaps at sill plates, around basement windows and where pipes and cables enter
• Weather-strip garage and bulkhead doors
• Keep mulch, firewood, stone piles and leaf litter back from the foundation; NC State suggests at least 12 inches of clearance for mulch
• Move stored items off the floor and out of cardboard

House centipedes

The house centipede (Scutigera coleoptrata) is the fast, flat, gray-yellow centipede with 15 pairs of very long legs that runs across bathroom and basement floors at night. Penn State Extension notes it hides in dark, damp places by day: under concrete slabs, in hollow block walls, around floor drains, in crawlspaces and in cardboard boxes sitting on slab floors.

Unlike most centipedes in Pennsylvania, house centipedes can live and breed year-round in heated buildings. Females can live several years and produce up to 150 young, per Penn State. They are predators, feeding on silverfish, carpet beetle larvae, cockroaches, spiders and other small insects.

Penn State notes that if you see house centipedes often, something they eat is abundant, and that can be the bigger problem. We look for the prey insects as well as the centipedes.

• Dehumidify basements and bathrooms and fix plumbing leaks
• Seal cracks in concrete floors and block walls
• Cover floor drains and sump pits with screening
• Get boxes off the slab and into sealed plastic bins
• Grade soil so water runs away from the foundation

Silverfish

Silverfish are silvery, carrot-shaped, wingless insects about half an inch long, with long antennae and three bristles at the tail. They run fast, including sideways, and squeeze into narrow cracks. Penn State Extension says they prefer cool, moist, dark places like basements, closets, bookcases and storage areas.

Silverfish feed on starch: flour, cereal, book bindings, wallpaper paste, glue and paper, and they also eat protein. In heavy infestations Penn State notes they can leave irregular holes and stains on books, papers and wallpaper. They live at least two to three years and produce more than 50 offspring, so a small population in a damp storage room can build up quietly.

Old paperwork, magazines and cardboard in a basement or attic storage area make good silverfish habitat. So do bathrooms with poor ventilation and the wall void behind a slow leak.

• Run a dehumidifier and repair leaky pipes and roof leaks
• Store dry food, papers and books in tightly sealed containers
• Cut clutter, especially stacked paper and cardboard
• Seal cracks and crevices along baseboards and shelving
• Use sticky traps to find where they are concentrated

Millipedes

Millipedes are slow, dark brown to black, rounded, wormlike arthropods with two pairs of legs per body segment. They often curl into a coil when disturbed. Penn State Extension says they normally live in cool, damp places under stones, leaf mold, mulch, compost heaps, grass clipping piles and brick paths.

Millipedes move in large numbers after heavy rains and when cooler weather sets in, and they can climb foundations several feet. They end up in garages, basements and first-floor rooms, often along the bottom of sliding doors. Penn State notes they do no damage and cannot survive long in the dry air of most buildings, usually only a few days. The ones you see inside are coming from outside.

The fix is outdoors. Penn State recommends removing compost and grass clipping piles and leaf mold near the house. Where mulch sits over plastic weed barrier, pulling out the plastic lowers soil moisture and raises soil temperature, both of which millipedes dislike. Inside, sweep or vacuum them up.

• Rake mulch thin next to the foundation and remove plastic weed barrier under it
• Move compost, clippings and leaf piles away from the house
• Install or replace door sweeps and seal window and door frames
• Keep gutters clean so downspouts do not soak beds along the foundation

Dehumidifiers, sealing and the order of operations

For all four pests, the work goes in the same order. Dry the space, close the gaps, remove the hiding places, then treat what is left.

A basement dehumidifier set to hold humidity near 50 percent, and drained to a sump or floor drain so it runs continuously, does more for crickets, centipedes and silverfish than most homeowners expect. A hygrometer tells you whether it is keeping up. Outside, check that downspouts discharge several feet from the foundation and that soil and mulch slope away from the house.

Sealing covers the sill plate where the house framing sits on the foundation, gaps around basement windows and window wells, utility penetrations, cracks in block and poured walls, and the bottoms of garage and bulkhead doors. Many of these are the same gaps mice use, so our page on mouse and rat control is worth reading if you are sealing anyway.

When treatment helps, and how C.R. Davis applies it

Treatment helps when populations are established indoors, when the moisture source cannot be fixed quickly, or when pests keep moving in from outside despite sealing. It does not replace fixing a wet basement.

We follow The Davis Inspection Standard. We identify the pest, because a millipede problem is an outdoor mulch problem and a silverfish problem is an indoor storage and humidity problem. We name the conducive conditions, checking damp walls and sill plates with a moisture meter. Then we place treatment where the pest lives, per the label: along the exterior foundation and entry points for crickets and millipedes, and in cracks, voids and harborage in basements, crawlspaces and utility areas for centipedes and silverfish.

We tell you up front how long to keep people and pets off treated areas, per the label, and when a follow-up visit makes sense. Homes that deal with these pests every fall often add the exterior work to a seasonal home pest control plan.

Related pests and service area

Spiders often follow these insects into basements, so see spider control for basements and garages if you see both. For the stink bugs and lady beetles that move into walls and attics in fall, see stink bug and fall invader control.

C.R. Davis III & Sons is based in East Pikeland Township near Phoenixville and serves Pottstown, Norristown, Downingtown and communities across Chester County, Montgomery County and Delaware County. Call (610) 935-9130.