Guess which one this is?
Seriously cool critter variously known as wheel bug (for obvious reasons--look at its back in the above photo), assassin bug, ambush bug. Pick one; they pretty much cover the basics of this beastie, here lunching on a small bumble bee.
The butterflies (hairstreak, buckeye) seemed completely unconcerned sharing the asters with it. Guess they knew it was otherwise occupied.
But it might be worth keeping an eye on nonetheless...