Black widow spiders are tiny spiders with red hourglass marks on the underside of their abdomen.
They’re 3/8″ in size, have 8 legs, round abdomen, shinny black in color, and they’ve no visible antennae.
Black widows are one of the most venomous spiders infamous for their painful bites.
Black widow spiders hide in cluttered spaces inside the house. And they can be hard to spot.
But the signs of black widow infestation are visible in their hiding places.
So, what are those signs? Let’s find them out.
3 Most Obvious Signs Of Black Widows
There are three signs of black widow spider infestation –
- Irregular webs at the ground level
- Black widow spider egg sacs
- Physical sightings of black widows
Irregular Webs At The Ground Level
Female black widows spin irregular webs near the floors.
These webs look messy. The female hangs upside down in them by exposing the red hourglass on her abdomen.
The red hourglass is a warning sign for it’s predators.
The reason that black widows spin webs near the ground is that they prey on crawling insects, not flies.
And the presence of black widows and their webs are a clear sign that there are other pests in the house.
Black widow spiders prefer to hide and spin webs in cluttered and dim places.
So, you’ll notice their webs at the ground levels in your basement, garage, crawlspaces, and attic.
Egg Sac
Another sign of black widow spider infestation is the egg sac.
Female black widow spiders will lay 250-300 eggs at a time.
They will spin a silken sac to pack these eggs into a spherical ball. This ball is the egg sac.
A fertilized female black widows will lay eggs in the spring, which is their mating season.
And in one season, the females can create 2-5 egg sacs containing hundreds of eggs.
She’ll keep the egg sacs in her web to protect them.
The egg sacs are whitish, have a rough texture, and they’re up to 0.5-0.6 inches in diameter.
The eggs inside the sacs hatch after 2-3 weeks.
The baby spiders will remain in the egg sacs for 26-30 days, and molt inside, before they come out of the egg sacs.
Spider eggs worsen the infestation.
That’s why professional exterminators look for and eliminate the egg sacs in the house to get rid of black widow infestation.
Sightings Of Black Widow Spiders
There’s no telltale sign of black widows in your house than their physical sightings.
These spiders are nocturnal. So, it’s hard to spot them during the day.
Black widows get inside the house from the outdoors.
They’ll crawl through the tiny holes and cracks on the walls and windows and hide inside the house.
You can also bring a black widow inside the house by bringing in firewood and cardboard boxes with a spider in them.
Outdoors, black widows will hide underneath decaying woodpiles, tree stumps, firewood piles, and underneath stones and decks.
Outhouses, barns, and sheds, are also some of the go-to hiding places for black widows at the outdoors.
Males Vs. Females Black Widow Spiders
It’s the female black widow spiders that are commonly sighted in homes and outdoors.
The male black widows are smaller than the females.
The males grow up to 1/8 inches (3-4 mm) in size, whereas the females are 3/8 inches (8-10mm).
There’s a difference in the abdomen’s shapes too.
The female’s abdomen is circular, whereas the male’s abdomen is oblong that elongates at the end.
Also, the males don’t have a red hourglass marking on their abdomen like the females have.
Instead of hourglass markings, the males have a row of red spots and white lines on their backs.
The female black widows are infamous for killing and consuming the males after mating with them.
Both the females and males are shiny black.
Black Widow Spider Bites
Black widow spiders rarely bite humans. They’re shy, reclusive and avoid human contact.
However, black widows will bite you in self-defense or when they or their egg sacs are threatened.
Black widows carry venom. And their venom is 15 times stronger than that of a rattle snake’s.
But black widow bites rarely cause fatalities.
You’ll feel intense pain immediately after the bite, followed by muscle cramps and headache.
People who’re allergic to bug bites can show symptoms like nausea, sweating, fever, aches, and chills.
You’ll also notice two fang marks on the bitten wound.
It’s vital that you seek immediate medical attention if a black widow bites you.
Before you reach the hospital, ensure that you wash the bite area with soap and apply ice pack on it to prevent the venom from spreading.
Do Black Widows Live In Groups?
Black widow spiders are solitary and nocturnal pests that don’t live in groups.
That makes them hard to detect.
Many black widows will even hide in the thinnest of gaps and cracks in the cluttered places of your home.
Female black widows come in contact with male black widow spiders only during mating.
But if you’ve found one black widow in your house, then chances are high that there are more.
If your house, with adequate food supply in the form of insects and bugs, is ideal for one black widow, then it can be the perfect hiding place for many more.
Black Widow Spider Control
Hiring professional pest control is always a good idea to get rid of black widows in your house.
If you’re going for DIY ways to eliminate them, then keep in mind that these spiders will get aggressive.
And you can expose yourself to painful spider bites.
So, it’ll be best wear shoes, gloves, and protective clothing while getting rid of black widows.
How To Prevent Black Widow Spider Infestation
Removing clutter inside places like basement, garage, and attic, and maintaining cleanliness in your home prevents the black widows from hiding in these places.
Ensure that there are no cracks on the windows, doors, and on the exterior walls of your house.
If you find any, seal them.
Spiders and bugs crawl through these crevices and sneak inside houses.
Also, remove any insects and pests inside the house.
Black widows hunt them. Insects present inside the home draw the spiders inside the house.
Keep your outdoors clean too.
Trim tall grasses and remove unnecessary shrubs.
Get rid of decaying organic wastes like leaf litter, tree stumps, and wood pieces. Store firewood properly so that bugs don’t make the wood piles their home.
While doing these steps, wear protective clothing, trousers, and shoes to protect yourself from spider bites.
On seeing the black widows, you can use a spider spray on the spiders to kill them.
Nang Chen is an Entomologist and Arachnologist who is associated with Vienna’s museum of natural history. He’s also a consultant with real estate groups, insecticide conglomerates and law enforcement groups as a forensic entomologist. Nang Chen holds an M.S. from South China University and he’s a regular contributor to our site.