The abdominal pattern looks like a Tegenaria and likely domestica, but can't tell for sure without magnified view of underside of palps. Both domestica and duellica have the pale spots at the edge of the sternum as seen in Vetter and Antonelli's paper on the Tegenaria seen here http://pep.wsu.edu/pdf/PLS116_1.pdf and in the photo I posted here . This one looks rather small and short-legged to be duellica, so if it has the spotted sternum it's a good chance it's domestica.

Everything you said is correct. Along with Steatoda grossa and many others, I keep and rear Tegenaria gigantea (that's the name BG uses) so that's the only reason I was confident enough to say it wasn't one. Range doesn't fit for T. agrestis... so the only one left is T. domestica. I would bet money on that... but would love to see proof. :)

All 3 of the Tegenaria I know of in the PNW are 'hobos', and since our freight mostly comes from the Seattle area, I watch for all 3 and they could show up in CO as well. We got one ad. male gigantea/duellica in a shipment of freight at the local carpet store, but no established pop yet. T. domestica is the only one established here in Wrangell that I have found so far.

Yep, I thought about mentioning that it could be possible to get a T. agrestis in Colorado, but really not very likely, in my opinion...not yet, at least (given another 10 years, I can see it happening). I'm not sure if you're saying that you personally refer to all three Tegenaria spp. as Hobos...as in a regional nickname, or...? The only one that is given the common name "Hobo" is Tegenaria agrestis, and that's the only one that has ever had a checkered past as far as necrotic bites. I believe it is the only spider in your state (AK) that is capable of any memorable human injury (necrotic lesions in some cases)...and is somewhat establish (I've read). I'm sure it's only a matter of time before Tegenaria gigantea is also well established, although that could take some time. In the meantime, though, I wouldn't doubt the occasional finding of them, whether in a shipment or not. They're big fellas, aren't they!

That's why I put 'hobos' in quotes--while only T. agrestis has that as it's 'official' common name, they are all 'hobos' by habit, readily hitching rides with human freight. Since T. agrestis is in Idaho, it's not that much farther to get to Colorado. Our high school science teacher got a box of freight with an adult female black widow in it (which he preserved), so it's not like a spider has to walk or balloon the entire distance. One of the things that got me started exploring AK spiders is the small, slow to heal, necrotic sore that developed on my husband's arm after being bitten by a 'big brown spider'. Unfortunately, he squashed the spider, so it couldn't be id'd. I've lost the old email from Rod Crawford, but I belive he said that both T. agrestis and T. domestica are well established in Juneau, Anchorage and Ketchikan, so I keep looking for T. agrestis, but have only found T. domestica here in Wrangell. Another potential culprit is Callobius pictus which is common here and is supposed to have a nasty bite, but I haven't found any volunteers to test it.

In perusing the Articles Forum, I found this 2005 map http://bugguide.net/node/view/33976/bgimage which shows 2 points in Colorado for agrestis, looks like the Denver area.

But these are probably your traveling spideys, no doubt found in shipments and such (after reading the caption under the BG range map, it does mention that). I don't believe they are established in Colorado by any means, but have begun their steady take-over of other nearby states like Montana, Wyoming, and Utah (if all those specimens were correctly identified, that is). But like I mentioned, given 10-20 years or so, they will probably be right at home in Colorado and other neighboring states. We can only hope that every specimen used as a data point is correctly identified. For instance, my gut and experience with both T. agrestis and T. gigantea tell me that the first image of T. agrestis on the Nearctic Spider Database is not a Hobo, but rather T. gigantea... but without having epigyne images, it's not worth the argument, ya know? I believe the last time T. agrestis was revised in English and for the nearctic ecozone was by Vincent Roth in 1968 (I have a copy). I'd say we're about due for a revision. Had I any pull in the business, I'd do it myself, lol. They started showing up in Washington in the mid 1930's (from England) and have just been steadily expanding their range ever since... in 1968 only WA, OR, & ID were affected, which is two more states in about 30 years. So no doubt this species will continue spreading until they run into states will high Latrodectus populations, in my opinion. Over here in the PNW, Steatoda grossa is one of the Hobo's biggest foes...but as the Hobo moves away from the coastlines, the S. grossa won't be around-- leaving the job of Hobo population control up to the Latrodectus and other certain theridiids. Those are just my educated guesses and may not necessarily be found in any publications (and could even be wrong!) I'm just speculating based on what I know.

Well, holy moley! I'm out of breath! And you're probably bored, lol. Sorry about that. I get carried away sometimes.

Here are some more T. agrestis specimens collected in CO:

Colorado

It seems it is likely established in that state now.

I never checked to see the data points on the Nearctic Spider Forum, oops. Thanks, John, for helping me see the light! Looks like Denver seems to be the root of the "infestation", which makes sense (more shipments and travelers than other cities?). All the counties that they were reported in seem to make a nice bulls-eye around the Denver area.

Well, guys... I'm convinced now. :) They do seem to be established in Colorado. Sorry for puttin' up such a fight, lol.

I, for one, am not keeping score. :) It's the give and take of information that makes BG such a valuable site. I just wonder when, or if, T. agrestis will ever become a permanent resident of Alberta.

Denver, Boulder, Lakewood, Littleton, Golden, and Lafayette - that makes a ring around the big trucking depot in Commerce City. I think Mandy must be right about these coming in via shipping - and we should look forward to data points showing up in Longmont and Castle Rock in the next couple of years.

> I think Mandy must be right about these coming in via shipping

Yes, and the Colorado collection data for T. agrestis most of them inside or around houses, so the species looks to be synanthropic.

Roth's 1968 publication says "in buildings and greenhouses". Plus, from personal experience, even just on my property, they are always either in the house or very NEAR to it in rocks and leaf litter. They have very interesting egg sacs, too! I've been waiting to mention it until the spiderlings are fully reared and I can post a life cycle submission, but they make a layered egg sac! First there's the inner sac that contains the eggs (usually approx 9mm in diameter), then the mother rolls it in dirt and leaf litter particles which adds another 3-4mm to the diameter... then to top it all off, she wraps it in white silk again. The final product is large and heavy and nearly perfectly round. The spiderlings are big and cute.