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Cheiracanthium mildei
(Long-legged Sac Spider)

Picture ID 15349

Picture of Cheiracanthium mildei (Long-legged Sac Spider) - In Retreat

Comments & ID Thoughts

Sac spider. So, I allow 4 or 5 of these to hang out in the house (that I can see...) If I see more, i let them outside. They mostly build the sacs in our bathroom. I've been letting them stay since they seem to be doing an excellent job of not allowing other bugs in the house (though, as I write this, I witnessed a tiny bug approach one of them and it literally sat there...). Its night time here so they are out. My husband thinks I'm nuts but I think they are interesting to watch while I get ready for bed. Anyway, the last couple days I've noticed two sharing a large sac. One I've seen come out and go in, and the other I haven't seen leave (pictured). This evening a larger sac spider tried to come near the sac and the smaller spider (who comes and goes) came running out and attacked him/her. I've never witnessed a confrontation from any sac spider (occassionally I've caught 2 together in a water bottle to let outside and they run from one another if they touch) nor have I seen them sharing a sac. Any idea what's going on? Just curious. Also, if it's not a good idea to let them stay in the house, please let me know. They seem pretty docile, but I have no idea.. I'll try to add pics of the two that got in the altrecation but not sure if I know how to. :-)

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The way that one is positioned in the web makes me think it’s a molt rather than another spider. I know nothing of their behavior though.


Maybe it was a male and female? Just guessing. I typically put these out when I find them. Because they wander in search of prey there’s a greater chance they might wind up in bedsheets or laundry where the odds of getting bit are greater. I don’t mind the occasional Cellar Spider (Pholcidae) or small Cobweb Weaver (Theridiidae) though as they tend to stay in one spot.

Additional Pictures

Picture of Cheiracanthium mildei (Long-legged Sac Spider) - Dorsal Enlarge Picture
Picture of Cheiracanthium mildei (Long-legged Sac Spider) Enlarge Picture
Picture of Cheiracanthium mildei (Long-legged Sac Spider) - Eyes Enlarge Picture
Picture of Cheiracanthium mildei (Long-legged Sac Spider) - Dorsal Enlarge Picture