brown widow spiders

Brown Widow Spiders (Arachnophobia Alert!)

Rae Spencer1 Comment

Several summers ago, I discovered black widow spiders in the yard. I became somewhat obsessed, torn between fascinated horror, sympathetic biophilia, and the urge to be a responsible homeowner and neighbor.

Though I’ve kept a careful watch, I haven’t seen many black widows in the last few years. In fact, I’ve congratulated myself for eliminating the kind of places they prefer. Which should have raised alarms. I rarely congratulate myself without stumbling, almost immediately, into awkwardness.

Here’s a zebra swallowtail butterfly, to make up for the photos I’ll be posting later.

Zebra swallowtails are large black-and-white striped butterflies with long “tails” on their hindwings. This one was photographed in flight as it approached a cluster of purple flowers.

Last fall, as we checked off our list of winter preparations for the yard, I found a cluster of delicately spiky spider eggs. They looked like burrs, and I made a distracted mental note to see if the internet could tell me what kind of spiders make burr-shaped egg sacs.

A pale tan egg sac in a spider’s web. The spherical egg sac has pointed tufts of silk scattered across its surface and is suspended by a few strands of silk.

Of course, my distracted mental note slipped into foggy forgetfulness. Then, while doing something completely non-spider related about two weeks ago, I found two more burr-shaped egg sacs in a messy web woven between the spokes of a bicycle I never ride. (The bicycle is stored in our Garage of Entropy, which we try to keep tidy despite the garage’s preference for chaos.)

This time I made a firmer mental note, and later that day an internet search told me exactly what kind of spider had made the fascinating eggs in my garage. A brown widow. (Arachnophobes, look away!)

A spherical, pale tan egg sac with pointed tufts of silk across its surface. Below and in the background, the orange hourglass-shaped mark on the underside of a brown widow’s abdomen is visible.

I think this is a good place for another butterfly…

Close up photo of an orange and brown painted lady butterfly. The butterfly is perched on a cluster of purple flowers.

According to bugguide.net (one of my favorite research resources), brown widows are an introduced species in the US: “It was introduced in Florida and has since been observed moving north through Georgia, and into South Carolina; it has also been officially recorded in California, Alabama, Mississippi, and Texas.” Obviously, this information is a bit dated. Our brown widows are two states north of South Carolina.

I use the plural “our brown widows” with a shiver.

Now that I know what to look for, the garage and yard are positively infested.

A brown widow spider hides in its disorganized web.

Bugguide.net says that brown widow spiders are one of the “most human-adapted” introduced species. What’s more, “It reproduces frequently and disperses rapidly, making it nearly impossible to control.” Each female spider, the information page notes, can produce up to 5000 young per season, and females can live as long as three years.

A gray-and-brown striped brown widow spider, with an orange hourglass-shaped spot on the underside of her abdomen, hangs in her web with four pale tan, burr-shaped egg sacs.

Despite a years-long effort to subdue my arachnophobia, these brown widow photos make me sweaty and anxious. How about a tufted titmouse, to break the tension?

A small tufted titmouse perches on a twig in the pear tree. The bird’s head, back, and wings are gray, its chest and abdomen are very pale (almost white), and there are tinges of pale orange in the feathers under its wings. All of its feathers are ruffled, including the crest of gray feathers on its head.

The question of whether or not brown widow spiders pose a public health risk is complicated. The Center for Invasive Species Research at the University of California Riverside provides the following information:

“The bite of a brown widow spider is minor in comparison to that of a black widow.  Although one frequently cited study demonstrates that, drop per drop, brown widow spider venom is as toxic as other widow species, venom toxicity is only one aspect when considering a spider’s bite potential. An African study with 15 verified bites demonstrated that the brown widow spider bite victims showed none of the classic symptoms of latrodectism, a response induced by neurotoxins in the venom of spiders in the genus Latrodectus (e.g., brown widows, black widows [L. mactans], Australian redbacks [L. hasselti], European black widow [L. tredecimguttatus], and New Zealand’s katipo spider [L. katipo]).  The reason for the weaker effect of brown widow bites on humans is possibly because the brown widow does not have or cannot inject as much venom as its larger relatives.  The two major symptoms of a brown widow bite were that the bite hurt when it was inflicted and it left a red mark. These two symptoms are not much different from the bite of normal household spiders.  However, there is one recent report of a verified brown widow bite manifesting in more severe symptoms that required hospitalization of the bite victim.”

Richard S. Vetter, https://cisr.ucr.edu/invasive-species/brown-widow-spider

The Texas Invasive Species Institute, from the Texas State University System, offers a similar appraisal:

“Currently, the brown widow spider does not pose the same medical concerns as the black widow spider. Bites from the brown widow do not cause the same symptoms as the black widow. Brown widow spider venom is twice as potent as black widow venom, it is believed the brown widow does not inject the same amount of neurotoxin. This, results in the decreased severity of symptoms in the form of cramping or nausea. This species is timid avoids human interaction. In fact, males and immature brown widow spiders do not bite at all. This species will fall to the ground in a ball as if it were dead as a defense mechanism, but should not be handled. Brown widow spiders bite out of defense, and it will only occur by mature females.”

http://www.tsusinvasives.org/home/database/latrodectus-geometricus

For one final illustration, here’s a couple of paragraphs from the University of Florida’s densely referenced brown widow information page:

“Symptoms: Black widow bites to humans may result in a variety of systemic symptoms (Sampayo 1943 and 1944). Typically, brown widow bites are not as serious as those of the black widow, and pain is usually restricted to the area immediately adjacent to the bite wound (Almeida et al. 2009, Foelix 2011, Suchard 2009). Also, approximately 15% of bites may be “dry” with no venom injected (Reyes-Lugo et al. 2009). However, some bites do cause the more severe, systemic symptoms characteristic of black widows (Arnold and Ryan 2009, Goddard et al. 2008, Müller 1993a).

“Müller (1993a) reported the incidence of the following systemic symptoms from 15 cases of brown widow bites in South Africa: generalized muscle pain and cramps (2), abdominal pain and cramps (4), weakness in legs and difficulty in walking (2), pain in regional lymph nodes (2), and raised temperature (2).”

Donald W. Hall, https://entnemdept.ufl.edu/creatures/URBAN/SPIDERS/brown_widow_spider.htm
A brown widow spider, identified by the orange hourglass mark on the underside of her abdomen and by the burr-shaped egg sac in her web, attempts to hide near the rusting axle of my old blue bicycle.

While some pest control sites list brown widow spiders as living in central and eastern Virginia, the Virginia Cooperative Extension information page about widow spiders lists brown widows as mostly occurring in Florida and Texas, noting that black widows are the primary widow species found in Virginia. So I’m considering this post as a sort of public service message for readers living in Virginia. Brown widows are here (and likely have been here for a while).

And now, after all of these photos of brown widow spiders and their spiky eggs, I think it’s best to close with a few images that don’t make me feel shivery and icky inside…

A small hawk with barred feathers on its chest and reddish-orange eyes perched in our pear tree just long enough to allow a single in-focus image.
Another photo of the zebra swallowtail butterfly. This time the black-and-white striped butterfly is sipping nectar from a cluster of purple flowers. The butterfly has long “tails” on its hind wings and a single row of orange markings on the exposed underside of the right hind wing.

Here are some links to articles that are more interesting and more important than what has been happening in my yard:

Note: I am implementing two practices in this blog post, practices I plan to continue. The first is evident in my photo captions, which are image descriptions for the visually impaired. The second practice will provide content warnings for my lists of links. I’m ashamed that I didn’t implement both of these practices earlier.

I would appreciate feedback regarding my image descriptions and content warnings. I’m happy to add more information and/or edit as requested, so please comment with suggestions.