Hi Christine...I appreciated your article about the Giant Swallowtails and especially that you noted they did not harm the citrus trees. Hopefully that will bring some awareness to people who commonly use insecticides to eliminate the larva.
These butterflies are also common visitors to my garden. When i had both a Lime tree and a Rue plant, i noticed that the Swallowtails showed a preference to lay eggs on the Rue and only used the Lime tree when there was no more space on the Rue. I no longer have the Lime tree but i increased the plants of Rue. The Swallowtails became heavily predated when the wasps discovered the Rue. Last year i tried an experiment. I grew Choisya ternata (which is not common in my area, although native to Mexico). I would see the wasps hovering around the Rue but never did they take a second look at the Choisya and i experienced 4 generations of peaceful and safe Giant Swallowtail caterpillers that grew to butterflyhood. I thought it was only a matter of time, but i was hopeful. I had grown only one Choisya t. and at the end of the rainy season, the Choisya dropped dead. I moved the existing caterpillars to a Rue plant nicely hidden in the patio area where they would have enough food to mature into pupahood. I think the Choisya t. did not have good enough drainage to survive our rainy season. Now i am starting new Choisya t. plants that i hope will survive in a place where there is better drainage. What charming caterpillars they are and such beautiful butterflies. I love having them in the garden.