[null and void]

I would suppose the fake antennae would be meant to confuse an enemy so said enemy would think the butterfly was watching him. But, so.....?

A predator wants to strike at the head. It's a quick kill, and if the prey tries to leap foreward to escape, the predator at least hits the body.

Striking the fake antenna gets a harmless bit of wing, or a total miss...

[okimhere]

A predator wants to strike at the head.

Now THAT is interesting! And the whole thing makes perfect sense now. Thanks, Nully.