I don’t think they can recognize the flyswatter, but they do seem to find a sudden increase in movement around them suspicious. Move slowly and strike from close up.

This actually brings up a good point that I never thought of before–it seems likely that if aliens have a religion, that religion will become a source of instant fascination to humans and will likely shake up Earth’s religious landscape a lot more than the simple existence of alien life would (alien life simply existing would not have much of an impact by itself IMO).

One of the founders of Reddit mentioned in an interview a while back that it was all bots when it started, to give the illusion of being populated when it was too new to have any users except the people who worked on it. From bots it came, and to bots it will return. The circle of life.