Penn State says Pennsylvania is outside the brown recluse native range. Any found are inside buildings, brought in by people, and extremely rare.
Penn State Extension: “Outside their native range (which includes Pennsylvania), brown recluse are restricted to buildings and are almost exclusively brought in by humans (such as when someone moves from an area where brown recluse are native). They are therefore extremely rare and localized.” Source
Yes. Penn State Extension says the southern black widow is found in Pennsylvania and the northern black widow is probably present too. Both are rarely encountered. Penn State Extension
“However, serious medical issues, such as dermonecrotic lesions and potentially fatal systemic symptoms, can occur, so confirmed bites should be monitored and treated with caution.” Penn State Extension
Size
Body about 7 to 12 mm (about 3/8 inch); females average about 9 mm and males about 8 mm. UC IPM says a recluse body is not more than 3/8 inch long.
How to recognize it
Six equal-sized eyes in three pairs. UC IPM calls this the most definitive feature, since most spiders have eight eyes.
The violin mark alone is not a reliable way to identify it
UC IPM's five-point check: six eyes in pairs, evenly colored finely haired abdomen, no spines on the legs, evenly colored legs, body no more than 3/8 inch
What the sources say
Venom: “Black widows and brown recluses are two types of venomous spiders in the United States.” (CDC / NIOSH)
UF/IFAS says males are often mistaken for brown recluses. The brown recluse has six eyes in three separate pairs, while the southern house spider has eight eyes bunched together at the front.
Ohio DNR says it is sometimes confused with the recluse, perhaps because it also has six eyes; recluses are much smaller, dull brown and have tiny fangs. UC IPM says the woodlouse spider's six eyes are in two groups of three (a recluse has three pairs) and it has no body markings.
Alabama Extension says the Mediterranean and Chilean recluses closely resemble the brown recluse and are difficult to tell apart from it; it has the same six eyes in three pairs. UC IPM says telling recluse species apart needs a high-magnification microscope and a spider expert. It is not native; Alabama Extension says it has been found in only a few small, isolated locations, and Ohio DNR reports it from buildings in several Ohio cities.
When spiders are seen in Pennsylvania
JanFebMarAprMayJunJulAugSepOctNovDec
5,336 records (GBIF, CC0 and CC BY).
If you see one in Pennsylvania
Keep your distance and do not try to catch or handle it. Feral swine: report to the Game Commission at 1-833-PGC-WILD (or 1-833-PGC-HUNT). Spotted lanternfly: report online or call 1-888-4BADFLY (PA Dept. of Agriculture). Venomous snake removal: call a local PFBC Waterways Conservation Officer. Nuisance wildlife: PGC region office; USDA-APHIS Wildlife Services 866-487-3297. Pennsylvania Game Commission
Brown Recluse Spiders. Penn State Extension. updated September 8, 2025; checked November 3, 2026.Quoted passages (2)
“Outside their native range (which includes Pennsylvania), brown recluse are restricted to buildings and are almost exclusively brought in by humans (such as when someone moves from an area where brown recluse are native). They are therefore extremely rare and localized.”
“However, serious medical issues, such as dermonecrotic lesions and potentially fatal systemic symptoms, can occur, so confirmed bites should be monitored and treated with caution.”
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