An Unexpected Visitor: Anise Swallowtail

Late yesterday afternoon, when we went out to do some work in the garden, I noticed a different looking swallowtail nectaring on the Echinacea.  Grabbing my camera, I started trying to capture it on "film".

The swallowtail was much more skittish than most of the other butterflies I see in the garden.  At first, it was hard to get within 15 feet of it, although after a while, I was able to sneak up a bit...

...especially when it started interacting with a tiger swallowtail female that was also nectaring on the Echinacea.  I don't recall ever seeing an aggressive butterfly before, but that's what this individual acted like.

He (?) would come up behind the female and sort of dive bomb her.  Then they would do a circling dance through the air (was it a male trying to initiate a courtship dance?).  Eventually they would both settle back down to nectaring again.

Neither my Kansas City butterfly guide nor my Peterson's Eastern Butterfly guide had this swallowtail in it, but I finally found a photo in another, nationwide, guide that I have.  I verified my identification by checking it against anise swallowtail in Bugguide.  Sure enough!  That was it!

Now I'm left to wonder if this individual was an accidental import on a plant (or firewood? or a vehicle?), or if it is simply a stray, far from its normal range in the western parts of the U.S.  I doubt I'll ever know, but I'm sure glad I happened to notice the visit of this charismatic stranger.