Learning to live with 'widow' spiders

Over the last two weeks, Ralph and I have been busy readying one of our rental homes for the arrival of new tenants.  In the process of clearing the yard of debris and cleaning up exterior and interior messes left by the previous tenant, I’ve encountered several brown widow spiders.

A brown widow spider guards her egg sacs and newly hatched spiderlings

 

Although black widow spiders are more notorious, they are only one of four members of the genus Latrodectus. The southern black, northern black, red, and brown widow are all in the widow family.  Of those four, the brown widow spider (Latrodectus geometricus) is the one most likely to settle around our homes, yard, sheds, boats and vehicles.

(Click here for more information and photos of the 4 widow species)

Black widow

Like its better-known cousin, a brown widow is easily recognizable by a brightly-colored hourglass-shaped marking on the underside of its bulbous abdomen.  Both spiders are about an inch long with legs extended, but unlike a black widow’s shiny black body, a brown widow’s upper body is grayish-brown with light white markings. 

Brown widow

I realize most people aren’t going to take the time to note subtle color differences between black and brown widows.  When they see a spider – a widow or most any other kind – their first reaction is to kill the eight-legged beast.  That’s unfortunate because of the 40,000 spider species worldwide, the vast majority – even widows - help humans by eating harmful insects.  In Florida, only 7 of the 900 species of spiders, which includes the four widows and three kinds of recluse spiders, pose a threat to people.

Comic by Bruce Thomas, www.mindcircuscomics.com

Although I know venomous spiders are capable of inflicting lethal bites, I also know the risk of that happening is minimal.  According to Dr. Steve A. Johnson of the University of Florida Department of Wildlife Ecology and Conservation, only seven people in the U.S. die from spider bites annually on average.  To put that figure in perspective, about 21 people die from dog bites each year while stings from bees and wasps are responsible for about 53 fatalities annually.

 

Entomologist, Fred Santana, of the Sarasota County Extension Agency states on a University of Florida IFAS website that widow spiders are generally non-aggressive and will retreat when disturbed.  Bites usually occur when a person sticks a hand in recessed areas or dark corners and inadvertently presses against a spider.

It was in just such dark spots where I encountered brown widow spiders at our rental house.  One was in the upper track of a sliding glass door, another outside in the recessed top corner of a double-hung window and a third was hiding underneath an aluminum railing in the screen porch.  In all three cases, I noticed brown widow egg sacs before I saw the spiders.

Brown widow egg sacs are easy to recognize.  Larger than a pea but smaller than a marble, each tan-colored orb is covered with small pointy projections that give it a prickly appearance.  Each egg sac – there are usually several – is secured within a three-dimensional conical-shaped web diligently guarded by the female spider who is usually hidden in a corner of the web during daylight hours.  Widow spiders are nocturnal and are generally inactive during days.

Brown widow egg sacs are prickly while the egg sacs of a black widow spider (below) lack bumpy projections

Photo credit: www.petmd.com

Because they were at one of our rental homes, I killed the spiders and crushed the egg sacs.  I knew my incoming tenants, who have young children, would not be want to share their new home with potentially dangerous arachnids. 

The thing is, spiders are everywhere and we need to learn to coexist.  Sure, we should take precautions like cleaning regularly and straightening away messes to prevent unnecessary interactions, but that doesn’t mean we should go crazy with fear and kill every spider we see. 

It’s important to learn about the creatures that share our ecosystem.  As knowledge grows, fear decreases.  Once we understand the habitat, behavior and lifecycle of these insect-eating critters we realize even ‘bad’ spiders like those in the genus Latrodectus, are not as bad as we’ve been led to believe.

Comic by Teal, www.chromatic-dragonfly.com