Spider Control in Southeastern PA: Fewer Insects, Fewer Webs

The spiders people find in southeastern Pennsylvania homes

Penn State Extension notes that many spiders native to Pennsylvania come into homes, mostly in autumn. Nearly all of them pose little risk to people and spend their time eating insects. Knowing which one you have tells you where it lives and what it is feeding on.

• Common house spider (Parasteatoda tepidariorum). Small, brownish, with a round abdomen. Builds tangled cobwebs in corners of ceilings, window frames, garages and under furniture. The most common spider inside houses here.
• Long-bodied cellar spider (Pholcus phalangioides). Tiny body, very long thin legs. Hangs upside down in loose, messy webs in basements, crawlspaces and damp corners, and vibrates the web when disturbed. Often called a daddy longlegs.
• Wolf spiders (family Lycosidae). Hairy, brown and gray, fast, and sometimes more than an inch across with legs. They hunt on the ground rather than in webs, so you see them running across basement floors, garages and first-floor rooms, especially in fall.
• Fishing spiders (Dolomedes species, such as the dark fishing spider). Large, brown and patterned, and easily the biggest spider most people see. They live near water and wooded creeks, and wander into basements, garages and boathouses. Homes near French Creek, the Perkiomen, the Brandywine and Ridley Creek see them more often.

Black widows: present in Pennsylvania, mostly outdoors

Penn State Extension says black widows are native to Pennsylvania. The southern black widow (Latrodectus mactans) is found here, and the northern black widow (Latrodectus variolus) probably is as well. Adult females are shiny black with a red hourglass or red marks on the underside of the abdomen.

They are usually outdoors, in undisturbed spots: under stones and garden timbers, in woodpiles and stone walls, inside water meter boxes, and under outdoor furniture. In garages and sheds they hide behind stored boxes and equipment. Penn State notes that bites come almost entirely from adult females, especially females guarding an egg sac, and advises care when reaching under stones, logs, firewood and behind undisturbed items.

Wear gloves when moving firewood, stone or stored items, and shake out gloves and boots kept in a garage. If you think you have been bitten by a black widow, contact a doctor or Poison Control.

Brown recluse: not established in Pennsylvania

Brown recluse spiders (Loxosceles reclusa) are the spider people ask about most, and the one least likely to be here. Penn State Extension lists 16 states where the brown recluse is established, mostly in the south-central and midwestern US, and Pennsylvania is not one of them.

Penn State says brown recluse spiders must be introduced to Pennsylvania, usually in boxes and household goods moved from states where they occur, and cannot survive the climate here unless they stay inside heated buildings. Isolated finds are rare and localized.

Most brown spiders reported as recluses turn out to be wolf spiders, cellar spiders, fishing spiders or grass spiders. A true brown recluse has a violin-shaped mark on the front body and six eyes arranged in three pairs, where most spiders have eight. If you have a spider you are worried about, catch it in a jar and we will identify it.

Webs point to insects: why spiders pick your house

Lots of spiders usually means lots of insects for them to eat. Cobweb spiders set up where flying insects collect, which is around porch lights, windows, soffits and garage doors. Cellar spiders and wolf spiders follow the crickets, silverfish, centipedes and small flies that live in damp basements.

That is why knocking down webs every week without changing anything else rarely helps for long. The spiders rebuild where the food is. Cutting back the insects, and the moisture and lighting that draw them, is what reduces spider numbers over a season.

If you see a lot of wolf spiders or cellar spiders in a basement, look at what else lives down there. Our page on camel crickets, centipedes and silverfish covers the moisture-loving insects that often feed them.

Stopping spiders at the exterior walls

Most spiders that end up indoors were outside first. The exterior of the house, the foundation line, eaves, window and door frames, and the gap where siding meets the foundation, is where we focus.

The perimeter work starts with removing webs and egg sacs along eaves, soffits and window frames. The gaps spiders and their prey use get sealed or screened: door sweeps, torn window screens, gaps around pipes and cables, weep holes and foundation cracks. Where an application is called for, it goes along the foundation, around entry points and at the eaves, per the label, rather than broadcasting it across the yard or through the living space.

Inside, we treat cracks and voids where spiders harbor in basements and garages when it makes sense, and sticky monitors placed along walls show which species are active and where. We tell you up front to keep people and pets off treated surfaces until dry, per the label.

How C.R. Davis handles spider problems

We follow The Davis Inspection Standard. We identify the spiders first, which answers the black widow and brown recluse question right away. Then we name the conducive conditions: a damp basement, mulch piled against the foundation, a woodpile beside the back door, bright lights over the entry, or gaps under garage doors.

Treatment goes where the spiders and their prey actually live, following the label. For homes where spiders and fall insects come back every year, a year-round pest control plan keeps up the exterior work across the seasons.

What you can do to cut down on spiders

A few changes around the house reduce the insects spiders hunt and the places they hide.

• Run a dehumidifier in damp basements and fix leaks, gutters and downspouts that soak the foundation
• Switch outdoor fixtures near doors to yellow bug-light bulbs, or move lights so they shine toward the door from a post rather than hanging over it
• Pull mulch, leaf litter and ground cover back from the foundation, and keep shrubs trimmed off the siding
• Stack firewood away from the house and off the ground
• Store basement and garage items in sealed plastic bins rather than cardboard boxes
• Vacuum webs, spiders and egg sacs regularly, then empty the vacuum outdoors
• Install door sweeps and repair torn screens before fall

Areas we serve for spider control

C.R. Davis III & Sons is based in East Pikeland Township near Phoenixville and serves West Chester, PA, Media, PA, King of Prussia and the rest of Chester County, Montgomery County and Delaware County. Call (610) 935-9130 to set up a visit.