3 Signs Of Black Widow Spider Infestation You Must Not Miss

Black widows are venomous, and they can deliver a painful bite if the situation arises.

These spiders are sneaky creatures that secretly get inside your home and cause an infestation. 

In this guide, you’ll find out what attracts black widow spiders to your home and where they hide.

You’ll also find three signs of black widow spider infestation that are easy to ignore, but you shouldn’t miss.

This post also reveals the steps you must take to remove the infestation. 

Keep reading.

What Do Black Widow Spiders Look Like? – A Brief Identification Guide

Black widow spider infestation signs

Black widow spiders are black, with the bulbous abdomen, and the females grow up to 1.5 inches or 38 mm in size. 

The males are smaller than the females. They grow up to 0.7-0.8 inches or 20 mm in size. The males are not as shiny black as the females. Their abdomen can be light brown. 

Both the male and female black widows have eight legs, with the front pair of legs being the longest. 

The black widow spiders are outdoor spiders that hide in places like woodpiles, underneath rocks, and foliage.

The ideal hiding places for these spiders in your yard are your firewood, mulch bed, and underneath organic debris like foliage. 

Look for the red hourglass shape on their abdomen to identify with certainty if it’s a black widow or some other spider species. 

The red hourglass shape on the underside of its abdomen is the unique identification mark on the black widow spider. 

On the female spiders, it’s more prominent than the males. 

But the male black widow spiders can have a row of red spots on their abdomen, but not specifically in the hourglass shape.

What Attracts Black Widow Spiders In Your House?

There are two primary causes of black widow spiders in your house –

  1. Presence of insects
  2. Inclement outdoor weather

Presence Of Insects

All spiders, especially the black widows, are predators. They hunt other bugs.

The presence of bugs in your home draws the black widow spiders and efficient hunting spiders like the brown recluse spider in your home.

Bugs release pheromones. Pheromones are a chemical with a smell that insects secrete to communicate with their kind.

Spiders can pick those pheromones. 

And spiders enter your home by following the smell. 

Most common places where bugs hide inside your home are cluttered places like your attic, garage, and basement. 

If your bedroom and kitchen are messy, they can be hiding places for bugs.

So, these places can also attract spiders. 

Black widow spiders will follow these hiding bugs inside your home, sneak inside, and hide.

Inclement Outdoor Weather

Extreme outdoor weather forces many bugs, including spiders, to look for a more temperate place to hide.

Excessive rain, heat, and cold can cause damage to their habitat. That makes the black widows look for an alternative hiding place.

And what do the bugs and black widows do? They sneak inside your home to escape the weather.

Black widows are effective crawlers. They can easily crawl through gaps, holes, and cracks thinner than their body size.

That makes the cracks on your windows, the gap between the door and the floor, the holes, and the openings around the utility wires entry point for black widow spiders.

Open chimneys and vents in the attic are also entrances for spiders and bugs like wasps and kissing bugs.

And when black widows get inside your home, they look for a place to hide.

Where Do Black Widow Spiders Hide In Your Home?

Black widow spider hiding

Before looking out for the signs of black widow infestation in your home, you must know their hiding places.

Those signs are not as evident or apparent as the signs of other bugs and critters.

So, they look for places where there are fewer to no human footfalls, filled with clutter, and get very less natural light. 

As black widows, and most spiders, are nocturnal, they undertake their hunting and searching for hiding places at night.

So, it can be hard to spot them during the day.

The most common places where black widows will hide are your garage, basement, attic, and storage room.

The worst part?

Black widows can also hide in your bedroom, especially underneath your bed’s storage section. 

If that storage section is packed with a lot of stuff, then black widows will inhabit it.

The problem arises when too many of these spiders are in your home.  

So, what are the signs of a black widow spider infestation? Let’s find it out.

3 Signs Of Black Widow Spider Infestation

Now that you know what causes black widows inside your home and where they hide, it’s time to find out the black widow infestation signs.

These signs are quite hard to spot because they’re not that evident. But with a little bit of due diligence and safety precautions, you can spot them. 

Here are the three signs of black widow spider infestation –

  1. Black widow spider webs
  2. Black widow spider egg sacs
  3. Black widow spider sightings.

Let’s get into each of them. 

Black Widow Spider Webs

Black widow spiders’ webs are unlike any other spiders’ webs. They’re unique both in terms of their weaving and their location. 

Black widow spiders spin haphazard and irregular webs. And they spin the silken webs inside the crevices or a few inches above the ground level.

It’s because black widows hunt crawling insects more than flying insects. 

Bugs like beetles, kissing bugs, stink bugs, ants, and roaches are their primary prey. Unlike the house spider, they’re not much fond of flies and mosquitoes.

However, black widows will eat them too if they land on their web. 

The black widow web is meticulously crafted despite looking like a bunch of silken threads.

It’s divided into three layers. 

The first layer, the strongest layer, protects the web from collapsing because of any debris or waste falling onto it.

The webbing is robust. You’ll hear a snatching sound when you break the first layer.

However, it’s not the second layer that traps the prey. The second layer has the densest webbings. It’s because the black widow spider uses it as a retreat and to wait for prey patiently.

The black widow spider hangs upside down on the second layer by exposing the red hourglass on its abdomen. 

It’s a defense mechanism. 

Predators in nature avoid bright colors because it’s a sign of venom. 

Exposing the shiny red hourglass marking by exposing the underside gives the same hint to the predators and keeps them away. 

The third layer is the stickiest portion of the web. That’s the layer for trapping the insects. 

When the insects get stuck on the third layer, the black widow spider picks it up by picking up the vibrations on the web. 

The black widow goes to the third layer, inserts its fangs, injects the venom, and paralyzes the prey before eating it. 

Black Widow Spider Egg Sacs

Black widow spider egg sac

Egg sacs are a clear sign of infestation. When you say there’s a bug infestation in your home, it means that bugs are breeding and laying eggs, causing an increase in their numbers. 

It’s the same thing with the black widow spider infestation. 

Egg sacs are a collection of hundreds of eggs spiders spin into one big ball. 

One black widow spider egg sac contains 250-300 eggs. And a female black widow spider can produce more than one egg sac. 

Hundreds of young spiderlings emerge from the egg sacs when the eggs inside the sac hatch. That intensifies the infestation. 

So, where do you find the black widow spider egg sacs? You find them at their hiding places.

Black widow spiders will hide their egg sacs inside the holes on the walls, stick them behind or underneath furniture, keep them inside cardboard boxes, or place them inside cluttered storage areas.

These egg sacs are half an inch in diameter, off-white or light beige, spherical, and have a notch at their tip. 

Black widow spiders spin these egg sacs with the same silken thread they use to spin their web.

The egg sacs take only two-three weeks to hatch. The young spiders remain inside the egg sac till they molt once and develop a strong exoskeleton to crawl and hunt.

The result?

Hundreds of baby black widows emerge out of these egg sacs worsening the black widow spider infestation in your home. 

Destroying these egg sacs is essential in eliminating a black widow spider infestation. 

Black Widow Spider Sightings

In all honesty, you can live in harmony with black widows even without knowing there are black widows in your home. 

But if there’s any sign which ascertains that there’s a black widow spider infestation starting to grow in your home, it’s the sighting of multiple black widow spiders inside.

When cleaning your basement, garage, or attic, you may come across them. 

Even if you see one black widow spider, there can be more.

Male black widow spiders will follow the female black widows hiding inside your home during the mating season. 

An overabundance of insects and pests will attract more black widows and spiders like the brown recluse and hobo spiders.

Symptoms Of Black Widow Bite

Black widow spiders bite if they feel threatened or get pressed against your skin.

Black widow spiders are also defensive towards their egg sacs. They’ll protect it when you try to remove spider egg sacs without appropriate safety measures.

During the egg removal, black widows can bite you if they’re nearby. That’s why it’s always wise to leave black widow spider removal in the hands of professional pest control.

Black widow spiders are venomous. They inject venom into humans if they bite them. 

Symptoms of bites include pain and swelling in the bitten area, nausea, fever, dizziness, sweating, and chills. 

Black widow spider bites cause pain, swelling in the bitten area, nausea, fever, dizziness, sweating, and chills.

Always see a doctor if a black widow spider bites you.

How To Prevent Black Widow Spider Infestation

To prevent black widows from taking refuge in your home, you must keep your yard or garden inhabitable for them. 

Keep your outdoors clean and free from debris, and store your firewood properly. 

Firewood piles and organic debris are hiding places for black widows in the outdoors.

Seal any holes, cracks, and crevices on walls, windows, and doors. Use mesh screens on the vents in the attic and use chimney covers during the summer months.

Use door stripping or window stripping to cover the gaps between doors and floors or window panels and sills. Black widows exploit these gaps to crawl inside homes.

Keep your home’s attic, basement, garage, and other storage sections clutter-free and clean. 

To protect yourself from black widow bites, wear shoes, gloves, and trousers while cleaning these areas in your home.

Spiders love dusty and messy places inside your home to hide. You can also keep spider baits and traps in these places to lure out any hiding spiders.

And finally, ensure there are no bugs and insects in your home. These are food for spiders. And the black widow spiders will follow these bugs to your home.


The black widow infestation signs are –

  1. Black widow spider webs
  2. Black widow spider egg sacs
  3. Black widow spider sightings.

This guide revealed where you’re most likely to see the signs of black widow spider infestation in your home. 

You’ve also learned the risks black widows bring and in what scenarios they can bite you. 

To prevent a black widow infestation in your home, keep your outdoor area clean, seal the gaps on your home’s walls, windows, and doors, and there are no bugs in your home.

Remember, black widow spiders are venomous. And they can get aggressive to defend their egg sacs while you’re getting rid of them.

That can lead to painful black widow bites if you’re trying to remove them without appropriate safety precautions.

Hence, on noticing the signs of black widows it’s always best to hire a pest controller to remove them from your home.