Depends whose faster. If Lucario uses Aerial Ace, then Heracross is done for, but if Heracross uses Close Combat, then same goes for Lucario.
I like Lucario better.
Lucario can't learn Aerial Ace and I wouldn't know anyone who would put that move on a Lucario if it did have it.
My mistake, I checked Serebii and Lucario can't learn it, could've sworn he could, but if that's the case, then Lucario will have to resort to Psychic. Otherwise, Heracross wins.
I'd rather rely on Blaze Kick. Since Heracross has a higher Sp. Defense, it will be able to live a Psychic from Lucario, but even then, it would most definitely live a Blaze Kick. Though I like Lucario more, I'd have to admit that Heracross would probably win, if no items are used.