Butterflies you won't see in your backyard in the USA
Here are some photographs of tropical butterflies from several
conservatories and butterfly houses that we have visited.
Here's something you will probably never see...the complete life cycle
of the African Citrus Swallowtail (Papilio demodocus).  The adult lacks
the "tails" found on most other swallowtail butterflies.
Butterfly Conservatory Links

(Whitehouse, Ohio)

(Columbus, Ohio)

(Pine Mountain, Georgia)

(Krohn Conservatory - Cincinnati, Ohio)
Check out this osmeterium.  Swallowtails all over
the world have this same defense mechanism.  
This gland is normally hidden under the skin
behind the head.  When the caterpillar feels
threatened, it quickly extends this snake
tongue-looking appendage releasing a very
pungent (stinky) odor!
Of course, as you've probably already guessed, the
host plants for the caterpillars are in the citrus fruit
family.  This one is eating lime tree leaves.