This page lists 28 spiders.
3 are venomous by official accounts. 5 are nonnative.
Not every species: no complete official list of Pennsylvania spiders exists, so this page covers the ones state and Extension sources name. How lists are built.
Which spiders can hurt you
Official sources single out these spiders in Pennsylvania, in their own words:
Medically important. “Two of the more medically important types are the black widow spiders, and the brown recluse spider and its relatives. These two types of spiders are rarely encountered in Pennsylvania.” Penn State Extension
Medically important, but only in buildings in PA and extremely rare there. “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
All 28 spiders
Venomous species first, then A to Z. Do not handle them.
“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)
“Two of the more medically important types are the black widow spiders, and the brown recluse spider and its relatives. These two types of spiders are rarely encountered in Pennsylvania.” Penn State Extension
What the sources say
Venom: “Black widow venom is principally neurotoxic, so at first a bite is almost painless.” (Penn State Extension)
Habitat: Black widows can be found under stones, in stumps or woodpiles, in vacant rodent holes, in the dark corners of barns and garages, and in outdoor privies and other undisturbed cavities. (Penn State Extension)
No official source we use states whether this animal is venomous. That does not mean it is harmless: do not handle it.
Size
Females 3/4 to 1 inch long, not counting legs (Missouri); 19 to 28 mm (Penn State); Texas A&M says the female body is more than 1 inch. Males about 1/4 inch (Missouri); 5 to 8 mm (Penn State).
How to recognize it
Round web about 2 feet across, built only by females; the spider rests head-down at the center, where a zigzag silk band (stabilimentum) runs vertically.
Abdomen an elongated oval, pointed at the rear, with two humps (shoulders) at the front.
Males are much smaller than females and rarely noticed.
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.
Yellow garden spider or Banded garden spider (banded orb weaver)?
Banded garden spider (banded orb weaver) Not stated
Missouri Department of Conservation: the banded garden spider is slightly smaller than the black-and-yellow garden spider, with a pointier hind end, and its abdomen has many thin silver and yellow crosswise lines and thicker black, spotty lines.
Photos show typical adults; individuals vary. Never get close to compare.
When spiders are active in Pennsylvania
Records of spiders in Pennsylvania peak in May to June and August to September. They show when people record spiders, not how many there are (about month bars).
JanFebMarAprMayJunJulAugSepOctNovDec
5,336 records of spiders in Pennsylvania by month (GBIF, CC0 and CC BY records).
If you are bitten or stung
Call 911 or Poison Help at 1-800-222-1222 right away. Poison Help connects you to your local poison center, any time of day.
Official advice from Penn State Extension:
Avoid spider bites: wear gloves for yard work and be careful reaching under stones, logs, firewood or behind undisturbed stored items. Penn State Extension
“Avoid bites by wearing gloves when doing yard work. Be careful when reaching under stones, logs, or firewood, or when reaching behind undisturbed household items such as cabinets, furniture, and boxes.”
Southern Black Widow Spider. Penn State Extension. updated September 8, 2025; checked November 3, 2026.Quoted passages (2)
“Black widow venom is principally neurotoxic, so at first a bite is almost painless.”
“It is probable that the northern black widow, L. variolus, is also present.”
“Two of the more medically important types are the black widow spiders, and the brown recluse spider and its relatives. These two types of spiders are rarely encountered in Pennsylvania.”
Brown Recluse Spiders. Penn State Extension. updated September 8, 2025; checked November 3, 2026.Quoted passages (1)
“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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