Roman parasites

Imagine the scene: city bus, school group, two children are chatting between children. One of the two - looking out of the bus at the city passing by - notices a writing on a wall and thinks aloud with his friend:

• 'Roman parasites'... But what does parasites mean?
  - I don't know. It will be an insult.
• .. - ...
• And who wrote it?
  - It must have been the Etruscans...

Picked up on a Turin bus and shared by Iacopo.