After Monarchs, Tiger Swallowtails are probably the most familiar and well-loved eastern North American butterflies. They are certainly eye-catching, with their bright yellow and black colouring and long-tailed wings. Flying from spring to fall, they are avid flower visitors. Females generally have more extensive blue on their hindwing than males. The Tiger Swallowtail caterpillar feeds on the leaves of trees and shrubs, including cottonwood and cherry, while adults nectar at a variety of flowers, and are pictured here on lilac and garden phlox.
The Eastern Tiger Swallowtail (Papilio glaucus) and the Canadian Tiger Swallowtail (Papilio canadensis) are similar in appearance, with the latter occurring farther north. Until 1991 the Canadian was thought to be a subspecies of the Eastern, but research has established that it is a separate species. The two species may hybridize where their ranges overlap. The Eastern Tiger Swallowtail produces two generations a year, while the Canadian, just one. Tiger Swallowtails are appreciated by birds as tasty morsels and missing wing pieces may represent close calls.
Willow House Chronicles 
Ooo, you got two of them to sit still!
During a hike on Saturday, I saw one and called over to E.g., “Hey, it’s — it’s that butterfly you hear about every year in primary school and never get to see!” But it didn’t stop for a photo.
Another good reason to grow lilacs (and Damesrocket?) .
By George, you’re right! I was thinking it was phlox, but it only has 4 petals = Dame’s Rocket. It has a nice scent, reminds me of narcissus maybe. I see it is yet another plant listed as a possible invasive.
There have been quite a few swallowtails around, so I got a few good opportunities. What I hate is when you get the picture lined up and just as you snap it, the butterfly closes its wings.