4 Poisonous Spiders in Pennsylvania (& 5 Facts You Should Know)

There are thousands of spider species in the United States. Pennsylvania has hundreds of unique species and only 4 species that are considered poisonous / venomous.

All spiders have fangs and most of them possess venom, but the bite of a spider very rarely has a serious impact on humans.

Those with compromised immune systems and other medical conditions could find themselves vulnerable to the spider’s venom.

In most cases, a spider will try and escape rather than bite.

Poisonous Spiders in Pennsylvania

The 4 spiders considered poisonous in Pennsylvania, include:

1. Northern Black Widow

Northern black widow spider

Scientific name: Latrodectus variolus.

Common name: northern black widow spider, northern widow.

The northern black widow spider has a glossy black belly with large red circles on the back side.

The hourglass, which is seen on the belly, is broken into top and bottom, which helps you distinguish it against the one-piece hourglass of the southern black widow.

The northern black widow’s venom is not as toxic as the southern.

It is also the females that have the harmful toxin, not the males. Males are considered completely harmless.

The mortality rate for northern black widow bites is 1% with the majority being small children.

If you are bitten by one of these spiders, you must visit the doctor, as everyone responds differently.

Bites include pain, which starts immediately upon being bitten and continues to get worse for a few hours. It usually subsides within 24 hours.

Latrodectus variolus Pennsylvania map
Distribution of northern black widow spider in ​​​​Pennsylvania

They are mostly observed in messy webs in woodpiles, undisturbed sheds, garages, and woodlands.

They are not aggressive and are not set on biting you. They are shy and more likely to try and hide. It will bite in defense if provoked.

The majority of sightings have been at night. If you see one, it is recommended to keep your distance.

2. Brown Widow

Brown widow

Scientific name: Latrodectus geometricus.

Common name: brown widow, brown button spider, grey widow, brown black widow, house button spider or geometric button spider.

The brown widow is smaller and lighter than the black widow with colors ranging from black and dark brown to tan.

They have an hourglass shape on their belly, which is usually yellow or orange in color.

They have a neurotoxic venom, which causes pain, vomiting, sweating, and muscle rigidity.

The good news is that their bites are not very dangerous and the effects are confined to the bite area and surroundings.

Their bites are not as dangerous as the black widow, due to the brown window not being able to deliver the amount of venom that the black widow delivers.

3. Southern Black Widow

Southern black widow

Scientific name: Latrodectus mactans.

Common name: southern black widow, simply black widow, shoe-button spider.

A mature female southern black window can grow to a body length of 0.51 inches (1.3cm) and 0.24 inches (6cm) for males, excluding the legs.

Females are black and shiny with red markings on the belly of an hourglass.

Juveniles are black or gray with white stripes and yellow and orange spots on their bellies.

Only the mature female is able to deliver a venom that affects humans.

The amount of venom delivered is dependent on the size and age of the female. They inject an alpha-tatrotoxin and can cause pain, swelling, nausea, and vomiting.

Deaths in healthy adults are very rare when bitten by one of these spiders. With more than two thousand bites annually, there have been no reported deaths.

4. Mediterranean Recluse

Mediterranean recluse spider

Scientific name: Loxosceles rufescens.

Common name: Mediterranean recluse spider.

A bite from the Mediterranean recluse spider can be dangerous, results in skin lesions. The good news is that there has been only one reported fatality from a bite from this spider.

They are often confused with the brown recluse and live in a number of habitats around the world.

If bitten by one of these spiders, it’s recommended you visit your doctor for treatment.

The Mediterranean recluse is often confused with the brown recluse. These can be identified for the violin shape on the top of the head, which is not obvious in this species. They are small and no larger than a quarter, including their legs.

Further Reading:

What To Do When You See A Spider In Pennsylvania

When you see a spider and you are confident that it is not poisonous, then you can carefully place a container over it and slide a piece of paper underneath.

Turn the container over, keeping the paper in place as you return the spider outside.

You can wear thick gloves as a precaution.

If you have seen a poisonous spider outside, it is advisable to keep your distance, but then they are in the home, you need to ensure you deal with it properly.

Keep a close eye on it and only catch and release if you are one hundred percent confident.

Alternatively, you can use a bug spray, which will kill the spider, so you can remove it safely without the risk of you or your family being bitten.

What To Do When You Are Bitten By A Spider

The majority of spider bites are completely harmless. Spiders will not bite unless they feel threatened. Bites usually only cause redness, pain, and swelling.

Unless you see the spider, it can be very difficult to ascertain what type of spider bit you.

Then there are some poisonous spiders, which have unwelcome side effects.

Signs And Symptoms Of A Spider Bite

The signs and symptoms vary depending on the type of spider that bit you.

Widow spider bites

Signs and symptoms of a widow spider bite can include:

  • Pain, redness, and swelling around the bite. This can spread to the back, chest, and abdomen
  • Nausea, vomiting, sweating, and tremors are common
  • Abdominal cramping, often misdiagnosed as a ruptured appendix

Symptoms from a widow spider bite can last up to three days.

Recluse spider bites

The signs and symptoms associated with a recluse spider bite include:

  • Body aches, chills, and a fever
  • Pain increasing over a few hours at the bite site
  • The bite would become dark blue or purple and has a red ring around it
  • The bite wound opens into an open sore, killing the skin around it

Symptoms from a recluse spider bite can last up to five days.

A bite from a brown recluse spider after 4 months

How To Treat A Spider Bite?

There are a few things you can do to treat a spider bite, which includes:

  • Washing the bite site in warm soapy water and keeping it clean
  • Cover the area with an ice pack to reduce swelling
  • Keep the area up above your heart where possible, to help reduce swelling
  • You can use an anti-itch cream to reduce discomfort from the bite

When to see a doctor

Always seek immediate medical care if:

  • You know the spider that bit you is a widow or recluse
  • You are unsure if the bite is from a poisonous spider but you have signs and symptoms
  • The bite would be growing
  • You are in severe pain with abdominal cramping
  • Your throat is closing and you cannot swallow or breathe
  • The bite site has spreading red streaks or redness

How To Prevent Spiders

There are a number of ways you can prevent spiders from coming into your home or yard, these include:

  • Seal all cracks in walls
  • Keep outside lights out or change to a red outside light that will not attract insects
  • Reduce the clutter in the home, yard, sheds, and barns. Spiders prefer quiet areas to spin their webs
  • Dust and vacuum regularly, including inside cabinets and cupboards
  • Try peppermint spray, eucalyptus oil, or tea tree oil, all of which are vile to spiders
  • Pull any outside plants away from close proximity to doors and windows
  • Use vinegar around doors and windows
  • Plant citrus plants. Spiders do not like the scent
  • Keep the lawn mowed and remove all leaf litter and debris
Citrus plants


Even the most poisonous spiders in Pennsylvania very rarely cause death. Their bites are painful and can cause redness, nausea, vomiting, and pain.

It is always recommended to seek medical care immediately if you think you have been bitten by one of the four poisonous spiders in the state.

Use preventative measures to reduce the risk of spiders moving into your home.

Further Reading: