@Ungoliant I have absolutely no idea sry, but could it be regurgitated stomach contents? I have no idea if tarantulas can even do that but if it's in a death curl maybe it threw up it's last meal or something.
I know my girl sometimes get white spots around her mouth after feeding (I could be wrong, but I think I notice it more when she eats larger roaches), but it's as simple as her grooming herself to get rid of it. I've never seen it to that extent though. That really doesn't look good. Could it have been something she ate?
@Ungoliant I had to have him euthanized. I have never seen this before. The white liquid almost reminded me of thin white-out liquid. He wasn't displaying any odd behaviors the last week either, his pedipalps were always touching the ground too.
When I saw him like this today the white mouth liquid was on his pedipalps too, and he was in a death curl position. I've had him for maybe 2-3 months, and he only ate 1 medium-sized cricket a couple weeks ago. He would always refuse food.
This is really strange. The only times I've known white fluid around the mouth is in tarantulas with nematodes but there aren't any worms in this pic. Still, was the tarantula wild caught? In that case I wouldn't exclude nematodes even if you don't see them.
Regurgitated somach fluids sounds like another reasonable guess. In that case something must have been wrong internally, though, since a spider should not regurgitate a meal, especially not if the only thing it ate was already a couple of weeks ago. A case of anal impaction where the spider "poops" from the mouth because that's the only way left??? (It actually happens in mammals, no clue if it can happen in spiders.) Did the spider poop?