Black Widow Spiders

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Lactrodectus hesperus Chamberlin and Ivie.

Spring and summer is when you find an over abundance of spiders around the house. In many instances, at least one of these spiders can be identified as the black widow .

The black widow spider is present in every state in the union and is found in Canada and South America. The males and females are distinctly different in appearance. The female is shiny black with a bright red hourglass shaped marking on the underside of the abdomen. A mature female, with legs extended, is up to two inches long with the abdomen ranging from 1/4 to 1/2 inch in diameter. The male is much smaller with its overall length less than one inch. It is usually lighter than the female in overall color and has light streaks on his abdomen.

The web on this species is also distinctive. The strands of silk run in many directions so the web appears as a concentration of irregularly arranged threads. The silk strand of the web is considerably heavier and stronger than those of other species that form similarly shaped webs.

The female hangs upside down in the web such that the red hourglass faces up. The egg sacs, which contain up to several hundred eggs, are most frequently encountered from May to October. The female typically stays with and guards the sac until the eggs hatch. The young spiderlings remain inside the sac for several days subsequent to hatching. Within a few days after emergence, the spiderlings release strands of silk out into the breeze and are carried off into a new territory. Most of these flights occur during the early fall months. Development from egg to adult may take from two to four months or more. A female may live a year or more after maturity. Males are sometimes killed by the female soon after mating, thus the name "widow" is attached to the spider

Control:

Periodically check areas in and around the home where black widows may occur. When discovered they can be most effectively destroyed by crushing or vacuuming the web and spiders.

Spiders also can be discouraged by increased lighting of darkened corners, such as by appropriate furniture arrangement or use of artificial lighting.

Insecticides can be useful for spider control but do not control all spiders. If you choose to apply an insecticide, do so to the dark, undisturbed areas where spiders are likely to produce webs.

Links:

Black Widow Spiders in the Low Desert

Ohio State University Extension Factsheet Black Widow Spider

Black Widow, Latrodectus hesoerus images of female and immature male

Suggestions for this page.
06/02/02
Considering the fact that I beleive we have several af these critters in our home,
I'd sure like info on the bites! Symptoms, what to do, how long I have to live, etc.!
The black widow spider produces a protein venom that affects the victim’s nervous system.
Some people are slightly affected by the venom, but others may have a severe response.
The first symptom is acute pain at the site of the bite though there may only be a minimal local reaction.

The local pain may be followed by localized or generalized severe muscle cramps, abdominal pain, weakness, and tremor. In severe cases, nausea, vomiting, faintness, dizziness, chest pain, and respiratory difficulties may follow.

The severity of the reaction can depend on the age and physical condition of the person bitten. Children and the elderly are more seriously affected than young adults.

In some cases, abdominal pain may mimic such conditions as appendicitis or gallbladder problems. Chest pain may be mistaken for a heart attack.

Blood pressure and heart rate may be elevated.

People rarely die from a black widow's bite. Life-threatening reactions are generally seen only in small children and the elderly.

Although bites are generally not fatal, they should be considered dangerous.
Contact your local poison control center immediately. In Phoenix call (602) 253-3334.
If possible capture the spider for identification.
06/06/02
I have 2 golden retrievers around 70 lbs. How would being bitten by a black widow affect them?
Black Widow bites can be dangerous for pets, and can be fatal to small dogs or cats.

06/08/02
It would be great to have an image of the spider from the top so that a person
doesn't have to turn the venomous beast over to identify the tell tale hour-glass shape :)
Great suggestion, will take a picture and put it up as soon as possible.
Should be up by late July.

06/27/02
I want to know what a young black widow spider looks like.
The young black widows are white in color and spread quickly after hatching.
We found a picture of an immature female, its in the view picture selection.

07/08/02
In what states are black widows more common?
Black widow spiders are found in all states except Alaska.
This link explains the 3 predominate species and distribution in the United States.
It has an excellent graphic showing the differences in pattern of red coloration on
the underside of their abdomen. Species in North America

07/14/02
Great site but it would be nice if you could be more detailed on where they are found in Canada.
It says in ALL states..but where in Canada are they found? be nice to know Thanks...and smiles
You're right , we couldn't find much information on black widows in the Great White North.
If we run into some information we will link it. Thanks for your suggestion.

07/18/02
Where are there nests usually located?
On the underside of ledges, rocks, plants and debris, wherever a web can be strung.
It's very common here in southwestern Arizona to find them in the garage or storage room areas and behind exterior trim.

09/16/02
Ok, so, I would really like to see what a Brown Widow's egg sack looks like. Apparently they're out in force in FL right now.
Brown Widow egg sack is is fawn coloured and spherical, with many points radiating from the surface, rather like a World War II marine mine.
This link at Florida Cooperative Extension Service has lots of info and a picture of egg sack. (Brown Widow Spider)

10/21/02
I've found 2 females, one dead in my living room (!) and one in the garage. It would be helpful to know what the males look like.
The adult male black widow is one-half to two-thirds the length of the female, has a small abdomen, and is seldom noticed. The male black widow does possess venom, but its fangs are too small to break human skin. The top side of its abdomen is olive greenish gray with a pattern of cream-colored areas and one light-colored band going lengthwise down the middle. The hourglass mark on the underside of the abdomen typically is yellow or yellow-orange and broad-waisted. The legs are banded with alternating light and dark areas.
Black Widow, Latrodectus hesoerus images of female and immature male

05/15/03
We just found a black widow female in our garage, not low to the ground, but in a window sill. I'm wondering what a widow bite looks like, 2 of my children have bedrooms in the basement and I'm in a panic!
The initial bite may feel like a pinprick, which may go unnoticed. At first, victims experience little or visible signs of the bite such as swelling. A red circular mark may appear about six hours after the bite. The initial symptoms may be progressive aching sensations, with muscle pain at the bite site spreading to the lower back, thighs and limbs. Symptoms often last up to 36 hours and lingering effects may last for several weeks.
Sorry couldn’t locate an actual picture of a bite.

06/25/03
Great site - thanks for all the info. We have just had a "black widow outbreak", and even though we cleaned/rearranged, they keep coming back to the same corner! What should I do?
With just a few black widows showing up around the home, killing them and crushing any egg sacks is usually the best control method. However, if they get carried away in and around your home a pesticide treatment may be in order.

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