Swallowtail butterfly | Swallowtail | swallowtail butterfly | Swallowtail hawkfish | swallowtail | Plate from Felder's work ''Reise Fregatte Novara'' illustrating the Swallowtail butterfly | Macleay's Swallowtail |
A study published in 2004 of the effect on Battus philenor in the San Francisco area found that gardens where the host plants were more than 40 years old, the gardens were as good as natural sites, where the host plants were less than eight years old the species was unlikely to visit, and in between the butterflies laid eggs but these had an inferior survival rate.