Wasps have been viciously attacking our Monarch Butterfly caterpillars they have to be cared for in containers to protect them until they can fly away. Even waiting on a bush - after hatching but before being ready to fly away - was too precarious.
A particular wasp species was getting more and more common and whenever we could we were out swatting them. We got some and missed others. Those that were hit then had to be quickly given additional treatment as they would soon compose themselves and fly off. Very tough creatures. The dead ones were fed to the local ants who removed them with vigour (see graveyard below).
Then the other day, I was walking in another part of the garden when a wasp nearly flew into me and then went up into the corner of the roof guttering and into the cavity behind it. Maybe it was a warning shot across the bow. I watched the guttering and saw wasps come and go. Out came the ladder and fly spray. In no time, numerous bodies were littering the guttering channel.
Now we don't see wasps patrolling the swan plants looking for a defenseless Monarch caterpillar to sting to death. It came as a surprise that the flow of predators was coming from our very own property. But for a lone wasp who nearly flew into me for whatever reason, they would still be on their killer missions.