Somewhat narrow black spider with brown legs and white marks and lengthwise red mark on abdomen - Latrodectus hesperus

Moved

… Lynette Elliott, 2 November, 2010 - 4:05pm

This

is L. hesperus.

Specimens east of CA in the southwest tend to be darker and more boldy marked, although plain, black adult females and light colored males are still found in the mix.

Also, this is one those exceptions I mentioned to you Lynette when describing the basal band differences in previous image a while back, this one being split as seen in the frontal view.

… Jeff Hollenbeck, 2 November, 2010 - 4:01pm

Thanks.

Good to get it settled, and interesting comments.

… Jerry Friedman, 2 November, 2010 - 5:36pm

Moved

Moved from ID Request.

Thanks for the ID. I didn't realize the males were such a different shape.

The guide page says male hesperus are "generally" light brown Does that mean "reliably"?

I hate to throw a pregnant widow out into the cold, but it might be time to evict the one behind my bookcase (if I can). There's a limit to how many of her children I want in here.

… Jerry Friedman, 31 October, 2010 - 12:06pm

Not sure about "reliably"

...but the fact that this one's black rather than brown was what tilted me toward mactans.

It's hard to cast children out into the cold, but there are limits to arachnophilia. I have a hesperus in a terrarium who just made an egg case, and the babies will be able to crawl out the terrarium's air holes if they can make it up the sides. Gotta decide what to do with them.

… Jack Owicki, 31 October, 2010 - 12:19pm

I'd think it's time to move them outside in both cases

I don't mind them outside, but I'd like to keep the inside of my house free of dangerous critters. =]

Also, male western widows can be 'black' sometimes. The comments on the image below say that the fused spots is typical of the adult western male widow.

… Lynette Elliott, 31 October, 2010 - 12:54pm

Male black widow

Looks like a male Southern Black Widow, Lactrodectus mactans.

For example, see:

Not dangerous to humans (although, of course, the adult female is).

… Jack Owicki, 31 October, 2010 - 12:33am

southern vs. western widow

I have a hard time telling these apart sometimes. I'm not sure which one this is.

… Lynette Elliott, 31 October, 2010 - 11:10am

I agree, Lynette...

...I came down on the side of mactans vs hesperus based on looking at some of the photos in the Guide, but I wouldn't claim a definitive ID.

… Jack Owicki, 31 October, 2010 - 11:14am