What's That Bug? does not endorse extermination

Subject: Spider eating a cockroach in LA
Location: Los Angeles
August 19, 2013 6:57 pm
Hi,
We recently started renovations on our garage here in Los Angeles. I couldn’t help but take a picture of this spider eating a cockroach on the side of our garbage can. I can’t figure out what spider it is. Can you help? Thanks! Megan. (in Los Angeles).
Signature: Megan.

Brown Widow eats Cockroach

Brown Widow eats Cockroach

Hi Megan,
Your spider is an introduced Brown Widow,
Latrodectus geometricus.  According to BugGuide:  “World wide in the tropical zone. 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.  Habitat Found around buildings in tropical climates.(1) However, it is an introduced species and is the most human-adapted of the species occurring in the South Eastern US. Its webs may occur anywhere there is sufficient space to make one. It may be extremely abundant on houses and other man-made structures (e.g., barns, fences, guard rails, bridges). It reproduces frequently and disperses rapidly, making it nearly impossible to control.”  As with other introduced species, which we consider Invasive Exotics, the Brown Widow might be contributing to a loss of species diversity by displacing native species where it has been introduced.

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What's That Bug? does not endorse extermination
Location: Los Angeles, California

4 Responses to Brown Widow eats Cockroach

  1. Dave Gracer says:

    Hello Daniel,

    Is this species medically important, or a threat to humans?

    Thanks,

    Dave

    • bugman says:

      Hi Dave,
      According to BugGuide: “NOTE: It is recognized that this particular species of widow is most likely not medically significant (not an immediate medical concern to those who are bitten). (Net Ref (4)) The brown widow produces clinical effects similar to that of the black widow but the typical symptoms and signs being milder and tending to be restricted to the bite site and surrounding tissues.” BugGuide also notes: “The brown widow is an extremely timid spider which has rarely been reported to bite.”
      When we saw your name on the comment, we thought you might be writing to tell us that it is edible.

  2. Pam says:

    Brown Widows are new to our yard; I saw the first sign of them last year. I am quite familiar with Black Widows. There are a couple of differences I’ve noticed between the two. Black Widows like the darkest places they can find. I will see them on my tomato plants and rose bushes, but usually down at the very bottom or deep inside. Brown Widows live all through my tomato plants, and I just found their spiked egg-sacs at the very top of one of my rose bushes today. I wouldn’t say they live in broad daylight, but they certainly don’t need much shade to make them happy. I’ve also accidently watered some lines of webbing from Brown Widows coming down from the roof to my plants, and saw them quickly run down the thread in response. I’ve never observed this with Black Widows. Black Widows usually cower. Either the Brown Widows are more aggressive, or they just don’t have the instinct to know that the hose water is not a bug. I’m not afraid of either as long as I can see them; it’s the ones I don’t see that bother me. Outside, they are welcome. They seem to have arrived at the same time as the American Cockroaches in my yard. I’d never seen either of them before last year. I live in the suburbs of Los Angeles, in the San Fernando Valley.

  3. I’ve been following the brown widow in Tampa Bay for some years now. I keep finding them in places which all seem to have a common denominator:

    Under an outside metal railing.
    Inside an electrical box with a cover.
    Under a water fountain in an outdoor breezeway.
    In the doorjamb of an unused vehicle.
    Under a park bench(!).
    Under a garbage can handle.
    Under a casement window hinge.
    In a drafty old wooden garage.
    Inside a galvanized chain link fence post.

    All of these places are outside, but not in the direct rain. Usually they’re nesting, and I notice the spiny spherical egg sacks in their nests immediately or even first. There’s sometimes debris and detritus in the nest as it has the appearance of being abandoned, but when I look closer, I see a female inside doing some spider house work. Notice that all of these places are places where one is likely to put their hand or skin.

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