When wet, they tend to turn a completely different colour. Below is Lot's Wife, who is mottled grey when dry, but turns distinctly green in rain. She's turned round on her silk pad (presumably in mild weather on Thurs 24th Feb) and is now upside down. Movement during the winter seems to be rare.
Below is Daniel. He's living in one of the most tit-infested parts of the woods, but is still alive. I arrived to check him just in time to eviscerate a flock of a dozen great tits, and on another occasion I chased off a large flock of long-tailed tits (or bumbarrels, as John Clare called them).
Conversely, here's the silk pad of a vanished larvae, presumably predated...