These spiders are very small, only about 4 mm. Their behavior seems to comport with their role as klepto's:

1) appearance: they look like a prey item that's already been wound up in silk, especially when...

2) they withdraw into their abdomen and hang by two forelegs as in this shot;

3) they move about -- and mate -- slowly, cautiously.

They are able to weave their own webs, sometimes within the webs of other spiders.