Why does this Symbol appear all over Catania, Sicily?

Catania gave me the impression that this oddly peculiar graffiti symbol is its distinct trademark. 

Interestingly they are all similar yet unique. Most of them were small and speckled randomly throughout the Italian city. 

It looks like a creature drooling over her beauty

But occasionally, a larger more elaborate designed version would appear: 

And here's a medium sized one :) 

  Those cool symbols weren't the only type of graffiti there though. 

But they were the most predominant street art and I hope they remain so since I left and continue to permeate the city.

Sometimes they appeared cute, like a face poking out from behind something

They are like Pokémon, gotta catch them all.

I do suspect a little bit that these symbols are associated with the mafia.

 After I started walking into a certain area which was highly saturated with them (yes, even more so than the normal already high density)locals shouted at me from their balconies to turn back! 

At least that's what I think they were doing? I didn't know any Italian. 

I'm such a redneck that I ordered tried to order a glass of vino and pronounced it vine-O