I found this rather large one on a climbing rose I had. I watched it flutter around, almost flirt-like before it landed. After I took several photos (many which did not turn out), it fluttered around again in my garden, landed on a Tecoma then vanished. I estimate the wingspread at about 4".
Thanks in advance,
Robin
Robin,
This is not the forum to use for identifications, we have a Bug and Insect Identification forum here: http://davesgarden.com/community/forums/f/bugid/all/
where you will have a much better chance of getting an insect identified.
Having said that, your butterfly is the Giant Swallowtail (Papilio cresphontes): http://davesgarden.com/guides/bf/showimage/1644/
Kennedy
