Symbolism, Imagery, Allegory
Cover Lassie's ears, because dogs are not our furry friends in Timon of Athens. In fact, they're not our friends at all. Calling someone a dog is a huge insult—just ask Apemantus. The Painter calls him a dog (1.1.202), and Timon says he'd rather hang out with a dog than the philosopher (4.3.200). But don't feel too sorry for the guy: he makes a comeback by calling the Painter's mother a dog (1.1.204)... and by calling Timon a poser.
So forget everything you know about dogs, and just accept that the characters in this play have some different ideas about man's best friend. Here, dogs are a unique insult: they come to signify the worst traits of mankind. Just as dogs bite and snarl, so do people; dogs are selfish and take for themselves before others can get anything... just like people. It's not a pretty picture.
Now, Timon, as we know, is barking up the wrong tree when he accuses Apemantus of being like a dog: it's his other companions who are the real dogs. He figures that out eventually, of course, so it's fitting that this is the insult he hurls at them after he's unveiled the dishes of stones and water at his banquet: "Uncover, dogs, and lap" (3.6.85).
Timon says it right to his friends' faces: they are nothing more than dogs. Want to take it further? Timon sure does: his friends are also "detested parasites, courteous destroyers, affable wolves, meek bears" (3.6.94-95). Ouch. Looks like his bite is worse than his bark.