Just ran across this study this morning. It does not include the heirloom zinnias, which I have also seen a lot of nectaring on, but it's interesting how popular 'Lilliput' was with butterflies compared to the other zinnia cultivars. If this file doesn't open automatically, just copy and paste it into your search line. It is free. Butterfly Feeding Preferences for Four Zinnia Cultivars, A University of KY study http://www.ca.uky.edu/entomology/dept/images/09yearganzinnia.pdf Rita Venable, Franklin, TN Williamson Co.