50 More Urban Species #46: House crab spider

[urbpan]

House crab spider Thanatus vulgaris

This spider is among the least "crabby" of the crab spiders. That is to say, its normal posture is less crab-like than other, wider-stanced crab spiders like the inconspicuous running crab spider or the goldenrod crab spider. They all similarly have longer front pairs of legs than rear pairs, with which they sieze insect prey. In the photo above, the spider adopted the crab spider pose after I manipulated her into place to get a head-on image.

The house crab spider is thought to be native to the central part of North America, in flat open areas, but is now found wild in California and Florida and other places. It can be found in houses, as the common name suggests, but the habitat this specimen was found in--a shipment of captive-bred crickets--was my clue to its identification. A search of online sources shows the frequent appearance of Thanatus vulgaris in pet forums, as a hitchhiker in shipments of crickets purchased as food for lizards and other creatures. The spider is not dangerous to pets or pet owners, and is probably regularly consumed with impunity by animals happy to have a switch from crickets (owned by people who didn't notice something different mixed with the usual chow). The spider pictured here has become a pet at the Franklin Park Zoo's Children's Zoo, for the time being. It has crafted an egg sac, but no spiderlings have been seen yet.

Are the spiders entering the cricket stream singly, as opportunists that drop in one at a time, or is there a permanent breeding colony of T. vulgaris that lives only within the microlivestock facilities, in amongst their limitless prey?

I found people trying to identify this spider from shipments of food insects here, here, here, here, and here.

The backyard arthropod project was very helpful in my quest, as was The Kansas Crab Spider Checklist.

Comments

[grace-batmonkey.livejournal.com]

she's so beautiful!

Our little spider!

[colleen donovan (from livejournal.com)]

We are going to have to put her on some glass (haven't i heard that in a song somewhere??) and take a good picture! It was too hard to get a good look at her just by sight, but you can clearly see her in that photo! I knew you could solve the mystery faster then me...all i could think of was a relative of the wold spider or some type of crab spider..cause she looked like the spiders you see in flowers but not as colorful. I had no idea there were "running crab spiders."

I am brainstorming names for her now. I hope her lifespan isn't very short.

[wraithfodder.livejournal.com]

I love that photo. Spider looks so big! :)

[wirrrn.livejournal.com]

Type of Crab Spider?! Called it! :victory mambo: :)

btw- Thanatus vulgaris?! "Common Death?!"

Nice work!

[tceisele.livejournal.com]

Excellent job tracking down other sightings. I think you have confirmed pretty solidly that these spiders are almost certainly an established population in cricket-breeding cages - if they were accidental introductions, I think we'd be seeing a lot more of other spider species in with the crickets, and not just this single species all the time.

[ndozo.livejournal.com]

If there are a lot of spiderwebs and/or cobwebs in my basement does that mean there are a lot of spiders and cobs? And if there are, what do they eat? Each other? Me when I'm down there? I'm hoping it's just a couple of prolific webmeisters but I think probably not. And I like spiders, but not so much webs in the face in the gloom of the basement. (I heard spiders webs can help cuts heal. If your fingers mending too slowly maybe get your spidey friend to spin out a bandage and see if it helps.)

[urbpan.livejournal.com]

Sure, it takes a spider to make a spiderweb. They can be eating each other to some degree, but probably there are little flies and stuff that you don't even notice.