I think we use to use some of those bug removers.. Cant think of the name we used but it worked great.. You get them in the Auto cleaning section
I'm pretty sure thats the name.. can get it at auto part stores... or some gas on a rag and rub away...
http://www.usautoparts.net/bmw/repairs/detailing/tree_sap.htm [FONT=verdana, helvetica, sans-serif]Gotta love the google! There's more, but I thought that would be enough to get you started. [/FONT]