TL;DR version: Brown Widows are becoming just as common if not more common than the infamous Black Widow in many parts of the Southern and Western US. Their venom toxicity is somewhat unknown, but most agree that they're still a medically significant spider.
Decided to write this up after making an interesting discovery in my garage today. Black Widows are as common as houseflies where I am, but the only place I've ever seen a Brown Widow was in Georgia. Behind a lawn chair that's been sitting there for quite some time was the tell-tale, distinctive egg sac of a Brown Widow. Chances are that many in the Southern and Western states have come across these curiosities in the past:
Note: NOT my picture.
No, a civilization of tiny, war-loving humanoids aren't planting land mines under the handle of your garbage can; you have Brown Widows in your vicinity.
What in the hell is a Brown Widow?
Well, that's a good question considering most don't even know they exist. The Brown Widow's scientific name is Latrodectus geometricus, which includes it in the same genus as Black Widows and Red Widows. Actually, there are several species of Widows living in the US: the Southern Black Widow, L. mactans; Northern Black Widow, L. variolus; Western Black Widow, L. hesperus; Brown Widow, L. geometricus; and the Red Widow, L. bishopi. The first three Black Widows are very common and their common names somewhat indicate their range. However, in many cases, the ranges overlap and you may find two different species in the same area. Respectively, the Southern BW is most common in the Southern and Eastern US; the Northern Widow is more commonly found northward but it's range also overlaps with the Southern; and the Western Widow is more or less relegated to parts of the Mid-west, Western and Southwestern states.
The Brown, on the other hand, is very much new to the USA. It's origin is still somewhat mysterious, but most experts believe they may have originated in either South Africa or South America. Nonetheless, they didn't make much of their appearance known until about ten to twelve years ago when they began being seen in Southern California and Florida. Since then, their range seems to grow more and more by the day. Just a few years ago, they weren't known to live in Georgia, South Carolina and even in Tennessee; yet, here they are. Anecdotal reports claim they're also now in Mississippi, Louisiana, and Alabama but those are currently undocumented. It's entirely possible they've been here much longer and were simply mistaken for Common House Spiders, but I'll get to that later.
Habits, Habitat and Appearance
The habits and habitat of the Brown Widow closely resemble that of Black Widows. They're commonly found under debris in dark areas like under rocks, piles of wood or bricks, etc.; unfortunately, they're also very common around areas of human habitation. In fact, Brown Widows seem to love the "company" of humans much more than their Black relatives. Some of the most frequent encounters are made around porches, patios, under outdoor furniture, under children's toys left sitting outside, and in and around outdoor trashcans. They seem to especially love making their webs under lawnchairs and under the handles of the aforementioned garbage cans or anything else where you put your hand
As far as habits are concerned, they're very shy creatures; much more shy than Black Widows, actually. They're not prone to bite even when protecting their eggs, much unlike Black Widows who will zealously defend their offspring. Nonetheless, the species WILL bite if mucked about with too much or if they happen to be trapped between something else and your skin (under your clothing, etc).
Appearance is where things get so iffy. To the untrained eye, the Brown Widow bears a striking resemblance to the Common House Spider, Parasteotoda sp. of which practically everyone has seen and there are probably several in your house as I type this. The Parasteotoda are incredibly common and of no medical significance, yet are closely related to Latrodectus and exhibit many of the same attributes.
Appearance of L. geometricus is as follows:
- Medium sized, normally topping out at no more than 1 to 1.5" legspan. Sometimes the actual size can fool you, though, because if a female has just fed or is full of eggs her abdomen might be be bigger than a dime.
- Tan to brown mottling on the abdomen, possibly with darker or red or white accents. Underneath the abdomen, though, is the tell-tale hourglass. The color of the hourglass can range from yellow to brownish-orange. This characteristic separates it completely from the Common House Spider.
- Tan-ish legs with dark brown stripes at each leg joint.
- The web is normally "hackled" but distinctive. It's often very strong for a spider it's size. At times, there's also a very strong "half cocoon" at some point at the upper region of the web where the spider goes to escape predators or any other disturbance. Their egg sacs are very distinctive, also, which you can see above.
Again, this species is very easily confused with the Common House Spider, so here's a little pictorial to point out the difference. All credit goes to the photographers as none of them are mine.
Edit: Instead of taking up so much space, here's an excellent summation of their appearance in pictures - http://sarasota.ifas.ufl.edu/ipm/brownwidow.htm
Also, here are pictures of the common and harmless Parasteotoda that it's often confused with. Lots of color variation, so just browse around: https://www.google.com/search?hl=en&...AaHk6QHk-o3fCg
Toxicity to Humans
Here's the fun part! Exactly how venomous are these critters? Unfortunately, there's still a lot of controversy over it. Some arachnologists submit that they're even more toxic drop-for-drop than the infamous Black Widow. However, they're not capable of injecting the large amounts of venom that a Black Widow can, so their "danger factor" isn't well documented. An entomologist at the San Diego Natural History Museum says that their venom is, "twice as potent as a Black Widow, but they only seem to inject half as much". So, doesn't that make it just as venomous as a Black Widow?
Other experts contend that Brown Widows and Black Widows have the same venom toxicity, but still agree that the Brown Widow doesn't inject as much. Still yet, being bitten by this species would be no fun at all. Considering it likes to dwell very close to humans, I think they should certainly be a concern. Currently, there's still a lot left of information left up to scrutiny.
So there you have it. Folks in the Southern and Western US may want to pay closer attention to those "house spiders" and cobwebs they have in the corner of their houses and garages. Again, I didn't really expect to see signs of Brown Widows here in South Carolina, but they're evidently here. I'll be hunting for them if I get the chance and it will certainly post up pics of whatever I find!