This butterfly is very fresh, probably emerged not too long before I saw it. It is nectaring on Queen Anne's Lace here, in an area of abundant prickly ash (Zanthoxylum americanum) shrubs, which is the only larval food source here for this species. It is amazing to remember that just a few years ago, these butterflies were unheard of in the Ottawa region, and now are seen every year, albeit in small numbers. From the underside this butterfly looks almost like a tiger swallowtail, but see it from behind and the black wings with the yellow bars are very different.