Only bug types??
Mmmm that would be hard. Anyway, in OU you can use UU and NU too so...
Scizor and Forretress are good OU bug types, so I think you should have them.
You could lead with a parasect with a focus sash and spore. That way you know you're setting one of your opponent's pokémon to sleep and then you can try to do something else with parasect. Something you must have is a rapid spinner, 'cause bug is weak to rock, and you'll loose a lot of HP just when you switch. Forretress can do that job, and can also set stealth rock!!
You can use heracross. It's UU now, but it is a good pokémon. But now you need something to take care about flying types, rock types and fire types...
You can teach stone edge to heracross, but make it scarfed or something, to be sure you hit the fire and flying pokémon first