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The venom of sac spiders
contains a cytotoxin—which means it kills cells—like the venom of a brown
recluse. Unlike brown recluse bites which can take 2-3 months to heal, most sac
spider bites heal much more quickly, although the reaction will vary greatly
from individual to individual. Typical symptoms of a sac spider bite include a
stinging sensation followed by redness and mild swelling. In a few cases, the
bite may blister and break, leaving a sore that can take several weeks to heal.
Sometimes the person will feel mildly ill. Sac spiders belong to the genus
Cheiracanthium and the family Clubionidae. They are quite small and easy to
overlook—about 1/4 - 3/8 inch long, with no conspicuous markings. The front legs
are longer than the other three pairs. Sac spiders are quite pale. A common
house species, the yellow sac spider is pale greenish, tan or straw coloured.
Other sac spiders are light brown. Sac spiders typically have darker mouthparts
and a faint dark stripe running lengthwise down the abdomen.
Normally, these are outdoor spiders, but sac spiders often invade structures.
Their numbers increase significantly in the fall when the weather turns cool and
their food supply disappears. If there are small insects available, sac spiders
can become established indoors. At night, sac spiders actively hunt their
prey—usually small insects. In search of prey, they run quickly waving their
forelegs before them. Indoors, they can be observed on walls and ceilings, but
drop to the floor to seek cover when disturbed. Sac spiders construct a silken
tube or sac in a protected area, such as within a leaf, under landscape timbers
or logs, or at the junction of a wall and ceiling, and they use this sac as
their daytime retreat. This is how the sac spider gets its name. These spiders
do not build webs. After mating, females lay 30 to 48 eggs and cover them in a
thin coat of loosely spun silk. The small, white, paper-like sacs are often
found in easily overlooked locations, along ceilings and corners, or behind
pictures and shelves. The female may guard these egg sacs and may produce
several egg masses during her lifetime. Inspect for sac spiders by looking for
sacs in upper corners of rooms, ceilings, behind pictures, on window moulding,
blinds or curtains. During the day, sac spiders may be inside these sacs so
vacuuming is an excellent method of control. Remove and discard vacuum cleaner
bags to prevent reinfestation.
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Reply: No 4 looks like a yellow sac
spider. 22 June, 2010:
Hi Glen,
I came across this spider sitting on top of my car late at night in Santa Cruz, CA. I was stunned at how white it was. It had no markings on its belly or back of any kind. I believe it may have fallen on my car since I was parked underneath a palm tree, and the dew around it looked slightly disturbed like it may have fallen onto the car rather than crawling onto the car. I would say it was about the same size as an average black widow. Do you think you can let me know what this is? Thanks Glen.
Julie |
Click for a larger view |
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Reply: It looks like a yellow sac
spider.
11May, 2010:
I was wondering if you could help me out. I have been randomly finding these spiders around my house since the beginning of spring and haven't been able to figure out what kind they are. At least 1 every other day or so.
This guy was hanging out on my roll of paper towels and actually let me take a few pictures. I just want to make sure they're not dangerous.
The first pic shows his size in relation the the roll of towels and the second is a close up. They've got almost a translucent looking off-white color.
Thanks! |
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Reply: No 4 looks like a yellow sac
spider. 3 May, 2010:
Hi!
I have a few more spiders I've taken pics of that I was wondering if you can identify. I'm sure you're a busy person, so don't feel obligated to get to them quickly---just whenever you can. Thanks so much!
1: I have no idea
2: This one was super small---kind of orange-y red and had indents on its abdomen, which I found interesting. It's on the lip of a jar, so you can see how small it is.
3. This one had the long leg hairs of a lynx, but wasn't sure??
4. I thought this one was a lynx....the light coloring and leg hairs
5. A crab? This one's missing a leg, but I wasn't sure if it was a crab because the front legs are usually longer, right? And this one's 2nd leg seems longer, so I don't know.
Anyway, thanks again. :)
Danna
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24 April, 2010:
Yellow Sac Spiders (two individuals) one was inside my house on the front door and the other outside near the front door on the siding. All pictures taken by me in southern NJ and free for anyone to use.
- Laura LeeNice pics, thanks, click for a larger
view - glen |
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Reply: This is a yellow sac spider and
can be medically significant. I have had a lot of photos of
these recently - glen 24 April, 2010:
Please help me understand what kind of spider this is...we have just moved to Virginia and keep finding these in the house...Thanks! |
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5 April, 2010:
I live on Long Island. I have these light colored spiders (yellow or green) that have infested my truck. I can't seem to get rid of them. I don't even know what kind of spiders they are. I used to park under a tree alot and I stopped that and figured they'd die over the winter. But all of a sudden they're back. Any suggestions or ideas?
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17 March, 2010:
Good afternoon, my name is Amanda. I have enclosed a foto of a spider I found in my closet last night. I wanted to find out what type it was or if it was dangerous at all and stumbled upon your site. Great site by the way! I've been on it for the past hour looking at fotos. The spider is nothing exciting but I find the color strange. Is it just some sort of house spider? Thank you for your time*~*Amanda |
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Reply:
This looks like a yellow sac spider and they can be medically
significant - glen
23 October, 2009:
Hey,
I live in Cleveland, OH and recently found an albino spider in my room. My backyard is the Cuyahoga Valley National Park so it's very common to see a lot of spiders in the fall, but not once have I ever seen an albino spider. I tried to look up information about them and got nothing. There are no venomous spiders, that I know of, in Ohio so I don't think it's a rare species. I have some great pictures of it that I attatched to this email, I had to make the pic smaller to send it but if you're able to, zoom in to see the transparency of the spider. If you know anything, could you please help me identify it?
Thanks,
Kara |
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5 September, 2009:
Hello, I love your site! I started taking pictures of spiders in my
house after my one year old son started getting what I think are yellow
sac spider bites. (Lymph filled blisters that rupture and take months to
heal.) So far your site has helped me identify 5 out of 6 of the spiders
I've found (including what I think is a yellow sac), and now I know
which are safe enough to catch and release, and which aren't worth the
risk (lest they escape and bite my son again). Except for the nursery
web spider who's picture was taken a few years ago (the most photogenic
of them all, and thanks to your site I know they're not dangerous), all
the spiders I caught were no bigger than a 1/3 of an inch... All the spiders I've photographed are from southern New Jersey. Please let me know if I've grossly misidentified any of my spiders. Feel free to post any pictures you like and thanks for making such a great site!
-Laura Lee |
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13 July, 2009:
Hello Glen, I ran across your page while trying to identify this spider
that I found on a plant in my living room. You can really zoom in on the detail
in this pic. Any ideas what it may be? I live in New Jersey, and the spider was
found in the springtime. I’d love to hear back. Thanks, Roland |
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9 June, 2009:
Hi there!
I live in Massachusetts, and stumbled across this spider a few days
ago in my kitchen window. To get a sense of its size, it's sitting on
one of the slats of a Venetian blind; I think the slat is an inch long.
Many thanks!
Michael :)
p.s. and for the record, I *didn't* kill it! |
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Reply:
Yes I agree it does look like a yellow sac spider and this is the sort of web it
makes. Click for
a larger view. glen
18 May, 2008:
first off i like to complement you on your great page. its very imformative and fun! I was hoping you could help me out. the past few weeks since the weather had been getting warmer i have been find one to three of these little freeloaders in my houes. i live in southeast michigan very close to lake erie. I decided to do a bit of research to find out what they are and I am thinking they might be yellow sac spiders. but they are not yellow. more a browmish grey. my biggest concern is my children. I have a 3 week old baby, a 19 month old and a seven year old. I just don't even want to think about my infant getting bit by one of these. my fiance thinks I am crazy and over reacting. i told him to call an exterminator or I was getting the kids out of the house till he did. maybe I am over reacting I don't know. I was hoping that you could tell me if this is even a yellow sac spider or just some harmless little critter. any help would be wonderful!! thanks so much.
Cortney, Monroe Michigan. |
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Reply:
Yes I agree it does look like a yellow sac spider. Click for
a larger view. glen
27 January, 2008
Good Day,
I live in Southern, Michigan on Lake Erie. We have spiders galore and they have started coming out since its April. Just wondering if you could ID this spider. I think it is a yellow sac spider after looking around on your site. Originally, I thought it was a young wolf spider, because we have lots of those. It was about 1/2 inch in total length, so pretty small, but its early spring.
Thanks,
Angie |
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Reply:
The yellow one looks like a yellow sac spider and the dark one like a broad
faced sac spider.
28 September, 2008
Hi Glen,
Attached is a photo of 2 spiders. I've come to the conclusion that the lighter one is a yellow sac spider. The darker one looks like a yellow sac - but darker. I've come across nothing online that says whether yellow sacs darken in fall.
We moved into our house in November and we've had somewhat of an infestation of the lighter spiders (yellow sacs, right?)
The long story:
I have a 2 year old. I never kill spiders. Before I found out they were yellow sacs I was putting them outside. When we found out what they were, my wife said "let me get this straight, we're putting the venomous spiders out in the yard where our daughter plays?" So that stopped. Then I got a terrarium but that was too creepy and filled up way too fast with yellow sacs. So then I got a bug vacuum (backyard adventures) and instituted a catch and release program where I would walk down the block a ways and free them.
Anyway. Spring was bad (2-3 spiders a day - mornings and night time) Summer was great - no spiders. Fall is shaping up like spring - except for these darker versions that seem to be showing up.
I worry about my daughter getting bit. I've been spraying a concoction of vinegar and coconut oil. That seemed to help in Spring to keep them away.
So here are my questions:
1. Can you confirm that they are indeed yellow sacs?
2. Can you tell me what the darker spider is in the picture?
3. Do you have any ideas how to politely ask the infestation to move outside?
Thanks for your time and your website. I will click on many google ads for you. Your site is a wealth of great info.
Sincerely,
Jeremy |
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a larger view.
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3 July, 2008:
This spider was crawling on the Bed last night. I would like to know what it is and if they are dangerous?
Thanks, Calvin
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30 June, 2008:
Hi Glen,
These are pictures of what may be a Yellow Sac Spider that was in our kitchen back in May. These things are turning up a lot, but that's not unusual. They appear every summer with no problems beyond a few family freak-outs. I'm the only member of my family that doesn't scream, jump, then attack when I see a spider. Feel free to use the pictures if you want.
--Damy
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10 May, 2008:
Hi Glen, I have a major infestation of this spider. I have removed
from my kitchen over 30 of them in the past week, by either removing
them and replacing them out doors .. well, that was at first when we
were being humane, then got freaked out and began vacuuming them up.
I've vacuumed at least 20 in the last 48 hours. Please let me know if
you have any insight for me on the type of spider and whether or not
they're dangerous and how to rid my home of them.
Sincerely, Sheila
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10 May, 2008:
Hi Glen, I think this may have been a Yellow Sac Spider. I know I've
already sent pictures of two different spiders that I thought were Sac
Spiders, but I'm pretty sure this is one. It looks very, very similar to
some of the Sac Spiders on your site. But I could be wrong. There is a
never-ending supply of spiders I can't ID around here. There are several I
can think of that I'm just waiting for an appearance from this summer. I
will certainly photograph them and send you the pics. Feel free to use the
pictures I've attached. --Damy
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10 May, 2008:
Hi Glen,
I think this may have been a Yellow Sac Spider that webbed down beside me
and started grooming itself while still dangling on a web. He finally
dropped down to the floor where I managed a few photos as he crawled
carefully around obstacles. I uploaded a video of this activity to Youtube:
http://www.youtube.com/watch?v=jIcwsSphExc. Attached are the best
pictures I snapped of him. Feel free to use them if you want. --Damy
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Reply:
Be careful, it looks like a yellow sac spider. I doubt that the little bites
would be from this spider though.
27 January, 2008
Hi guys. Thought maybe you
could identify this spider. I could probably get a better photo if I try a bit
harder. We have them in our house in Champaign, Illinois. My wife has had
little bites before and we wondered if they were spiders. Generally we like
them but wanted to be sure it was nothing to worry about. Thanks a bunch. Jesse Click for
a larger view.
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3 September,
2006:
Hi, Just been looking at the website and it is very
impressive. The pictures I have attached are of a spider found
in a bedroom in my house in Poland. Being British, I have never
seen anything like it before and wondered if you could identify
it for me and let me know if it is dangerous. Many thanks
Regards, Sharon
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Reply:
Be careful it looks like a yellow sac spider.
28 August, 2007:
Hello! I've loved your site for a long time, but hadn't been able to find it
for awhile. Thankfully I found it again! I've done well at not killing
spiders in and around my house the past year or two. I've learned how to
co-exist with them nicely(they eat the earwigs and the flies, which I HATE,
so the spiders are now my friends). My main question(to make a
long email longer) is about a spider I found in my bathtub last night. After
looking on your site, I'm thinking that it could be a Yellow Sac Spider, and
if it is, I feel awefully silly about not trying harder to get it out of my
house at least. Just wondering if you could take a look for me and let me
know what you think? And, if I see it again, what would be the best course
of action... I'm assuming removal from the house- which I was going to do
last night, but got creeped out by the darn thing and by the time I went
back to try and capture it, it was gone. I have 4 kids and 2 dogs, and
wouldn't want anyone getting too close and getting hurt by it if it is a
Yellow Sac Spider (or any other harmful spider). Any help would be Greatly
appreciated!
Heather, Colorado Springs, CO
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Reply:
Be careful it looks like a yellow sac spider.
8 July, 2006:
Hi, My kids found this spider in the house and asked me to take it's
picture. I thought it would be neat for them to find out what kind of
spider it was. If it helps, we live in western Michigan. Thank you in advance
for any help you can give us. Kim Click for
a larger view.
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13 June, 2006:
I live in Plymouth, MA and I seem to have a spider problem. I see at
least one of these a day in my house. Sometimes 2 or 3 per day. One
morning there were 3 all within a ten foot radius at once. Is it normal to
see this many? I have done some research online and would
just like to get some sort of confirmation. I believe they are sac
spiders? To be honest this scares me because I have also read that
they are the most common cause of spider bites in the US. They seem
to confine themselves to corners and where the walls meet the ceilings,
but have also been caught crawling across walls and
ceilings. They also fall towards the floor when disturbed. Are these
dangerous and should I be concerned? How can I minimize their
existence inside my house?
Thanks,
Kevin Olson, Plymouth, MA |
Reply: Yes, that is
a Cheiracanthium
species sac spider, which ARE medically significant. Nathan
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Reply: First one could be a yellow
sac spider:
http://www.srv.net/~dkv/hobospider/yellosac.html
and they can cause a painful bite. |
30 May, 2006:
Good morning, I live near Burlington, Vermont, USA. Love the sight, though it gives me the willies like you wouldn't
believe.
I found three spiders recently, and would like to know if anyone
can help with identifying them. (Please feel free to eliminate any pics you feel are
extraneous.) Sorry about the quality of these two, it was full dark, and I
was releasing the next spider, when I saw this one. Sitting on a
2x6 board ... .5" - .75" longish
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Reply: The closest match I could
suggest is the yellow sac spider. Check
this page
to compare.
12
November, 2005:
Dear Glen, I have a little bit of a strange situation. It is going to
sound like a joke, but I promise it is not. I am in the Philippines and I have a
small baby monkey that was bitten by a spider. He was trying to catch it to eat
it and apparently the spider was not willing to go without a fight. It
definitely bit the monkey because the monkey rubbed his hand for several minutes
after the bite. I need your help in identifying the spider to know if there is
anything I can do or should do to minimize the effects of any venom that might
be involved. I really appreciate your help. Thank you, Robert Ross |
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Reply: Be careful with this one as
it resembles a yellow sac spider which can give a nasty bite.
Click here for more info.
23 October, 2005:
I found this spider above my fridge and I don't know what it
is? its about the size of a dime and very fast. please help.
Thanks, Josh. |
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Reply: That is
Cheiracanthium inclusum, the yellow sac spider, which is
medically
significant. - Nathan Hepworth
17 October, 2005:
PS. After seeing your site, I found the species of spider
that live all over our home. They appear to be sac spiders
(again, see photo), and it seems that maybe they aren't
necessarily the best candidates as roommates. |
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20
July, 2005:
Hi, is this spider a yellow sac spider? We live in
Philadelphia, Pa. Any help would be appreciated. Thanks, mike
Click for larger view. |
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Reply: This is a sac
spider, Cheiracanthium mildei. See this page:
http://www.bugguide.net/node/view/3366/bgpage Nathan Hepworth |
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23 June, 2005:
Ok I took some better pics little
boogers are hard to take pics of anyways maybe these will help I
live in Ottawa Canada maybe the region may help in determining
what type it is like I said I have never seen one like this before
Thanxs again!
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Reply: This picture has been posted
before, on this page:
http://www.spiderzrule.com/spiderphotos04.htm
And there is an ID , in red text, above the image. The spider
is Cheiracanthium inclusum, the yellow sac spider. Go to this
website for more info:
www.hobospider.org. A yahoo search on the scientific name should
give you some more pics and/or info.
- Nathan Hepworth. |
4 March, 2005:
Hi, my name is Sonia. I have attached a photo of the spider
that keep showing up in my basement. I'm just wondering if you can
tell me what kind they are and if they are dangerous. I'm concerned,
because I have a 1 1/2 year old daughter that had spotted the last
one and tried to pick it up. I searched up and down your website and
couldn't find anything that looked like this. It has a reddish clear
body.
Please Help!! |
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