The quickest way to see their "not harmless" side is to kill one. As with many colony wasp species, other individuals will smell volatiles released by the corps

The quickest way to see their "not harmless" side is to kill one. As with many colony wasp species, other individuals will smell volatiles released by the corpse, and respond by seeking out whatever killed their sister in order to strongly discourage any further such liberties. So, best leave them well alone. (Unless you're me, and willing to risk a sting in order to get macro shots, although it's not all that much of a risk as long as I'm not near the nest. Never have found any hornets yet, though, sad to say, not even D. maculata.)