We’re lumping two groups of characters together here. We might be playing fast and loose with our symbols here, but it seems to us that these outsiders serve pretty much the same purpose in the novel. They’re vagrants. Thieves. Scary, dirty, probably smelly people. Terrorizing the townspeople seems to be their only purpose in life. The gypsies and the thieves help us to understand that Highbury is a social entity which needs to be protected from the dangers of the outside world. It’s lucky that there are big, bad men like Frank Churchill to fight the gypsies off with a walking stick.
Wait a second, though, aren’t the gypsies just little kids? And isn’t it only Mr. Woodhouse who’s scared of the chicken thieves? Well, yes. You’ve got us there. As it turns out, the only people who seem to need protecting are actually pretty silly themselves. Harriet and Mr. Woodhouse might be justified in their fears of the gypsies and the thieves, respectively. Or they could just be melodramatic.
Austen allows her descriptions of encounters with outsiders to hover on a knife’s edge: the gypsies could, after all, become a threat to society. They could also be perfectly harmless – which would mean that Harriet and Mr. Woodhouse’s fears (and, by extension, Highbury’s fears) are over-exaggerated. We’ll leave it up to you to decide.