Nicholas, cloudless sulphurs love red flowers, also rose and coral flowers. Here's a female on turk's cap, one of their favorites -

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And here's one on rose pentas -

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Another favorite is Salvia guaranitica, which is electric blue -

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Giant swallowtails really like lantana, but they also like Mexican sunflowers and most of the same flowers as all butterflies like. They especially like tropical milkweed -

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Sherry

Hi Nicholas,
I don't get many Giants in my yard, so I cannot address their preferences. However, I do get a lot of Cloudless Sulphurs, and I know from experience that they love tubular shaped flowers best. Mine really go crazy for my Pineapple Sage. The Black and Blue Salvia is great for them too.
Angie

YYYYYYYAAAAAAAAAYYYYYYY!!!!!!!!!!!!!!

Congratulations! How beautiful! Is that bougainvillea?
Liz

Thanks everyone I finally got to see one . Yes Liz it is bougainvillea. Here in southern California there is not much frost. The butterflies love it i've seen Monarchs, western tiger swallowtails, anise swallowtails, Gulf frits, painted ladies, And now Giant swallowtails sucking there nectar. I have Giant Swallowtail eggs, today some hatched I'm so excited!!!!! I'll post some pics later.

Nicholas

Beautiful shot Nicholas! Gotta love the Giants!
Angie

I think that both of these butterflies will use many different flowers. If you want more of both you will need more host plants, in my opinion. Clearly the Cassia should attract sulphurs. I don't know how effective rue is where you are.

I would do some research on what they use as host plants. If you have host plants you will have the butterflies that use them. Hate to generalize too much, but the more host plants you have the more butterflies you will have also.

Love those photos! MissSherry, The Giant Swallowtail and the Sulphur are just unbelievable!

I saw my first Giant Swallowtail this year out at an forest preserve! I will be getting some Ruta graveolans when I can.

Thx for the beautiful pics all!

Yes, BG, giant swallowtails show up further north than one might think, and if you have their host plants, you can get eggs, something I haven't gotten all year! :(

Sherry

Beautiful pictures! Where did you find the eggs. I looked under the leaves of the 1 milkweed plant I have, I don't see any eggs. I would like to find eggs to show my grandniece & nephews.

Great shots, Nicholas:) An orange tree somewhere in the yard will serve well as a host plant for Giant Swallowtails.

The big old female GST was in my yard again yesterday, checking out a whole bunch of plants, and fluttering around the rue. She looks like she tries to oviposit but I don't think she ever lays any eggs. Need to go out and check this morning to be sure, but I doubt it.

So I've made 3 observations of P. cresphontes last year, and 2 this year so far, which is exciting because it is a rare species in Mass. From what I've observed, they have nectared on the Monarda fistulosa, tall Zinnias, Phlox paniculata, and Verbena bonariensis.