I've already killed the 3 I could find, and it's been more than a few days in-game and haven't seen them again.   The widowlings have respawned, but not the big ones.   Considering how rare venom is, I still don't even have enough to make a Widow dagger yet.   

I killed all three that I know of as well. Currently 5 in game days have passed with no respawn. 

I found there are actually 4 of them total.  

And from what I can tell, they do respawn....but only if all of them are dead, and only ONE will respawn at a time, and it's random which one it is.  

I killed all, but the car battery cave one. Do you know where the entrance to the cave is by any chance? I couldn't seem to find it. 

8 hours ago, Eggos said:

I killed all, but the car battery cave one. Do you know where the entrance to the cave is by any chance? I couldn't seem to find it. 

The entrance is a bit tricky, it's kinda south-east of the Car Battery, and it's a hole in the ground in the side of a small overhang that has a rock blocking it's entrance that you need to blow up. (The rock is tucked into the hole)  Inside is a cavern, and in the cavern is a hole that you can drop into that drops right down to where the widow is.  

Also, one way you can get close to it, is to use resource tracking on widow venom or fangs.

I tried resource tracking after killing the third, and nothing showed on the map. But I'll see if I can find that cave, thank you.

Sean - thanks for sharing ! I'm having a heck of a time finding this cave too. Anyone mind posting a screenshot? Or are there other reference points near it? 

I killed all 4 widows, dose anyone know how long it takes for them to respawn

Here is a screen shot 

Hi, i killed all black widow, and i've no respawn problem. They came back after three days above average, sometimes few longer. Just one never reapper, the one under the cabin.