That might have been these things
Actually, I would think it's more likely it was honeybees. It would after all, be much more difficult to transport the hornet nest with the catapult, and it would be impossible to breed them like they could with honey bees. Even if they were lucky enough to find one in a tree nearby, they'd still have to carry it from the tree to the catapult, and even if it could successfully be fired, the paper mache' nest would be too light to travel that distance without being stopped by the wind resistance. If they used honey beex, they could put them in convenient wooden packages that would split open upon impact, and even though they are more dossile than hornets, the nest being destroyed would be enough to anger the bees enough to sting like crazy.