The gorgeous purple-flowered plant is Shale-barren Aster, Symphyotrichum oblongifolium, a native that has made its way into the nursery trade. It truly is a fantastic plant, and a total bug magnet. Shale-barren Aster, in this ornamental form, becomes a small bush bedecked with hundreds of blooms, and it flowers nearly to winter. Mrs. Mantis knows well the allure of these flowers for all manner of pollinating insects; that's why she lives nearly her entire adult life hiding amongst its flowers.
As you've probably deciphered from the name, Chinese Mantids are not indigenous to the Americas; they are another in a long list of Asian imports. This species was intentionally brought to North America in the mid-1890's, ostensibly as a control for "pest" insects. In my view, the mantis itself has become the pest, and any benefits from them are far outweighed by the damage they do.
The primary issue with Chinese Mantids is that they are indiscriminate in their choice of victims. About anything that can be seized and overpowered is fair game. This includes butterflies, all manner of invaluable pollinating flies, bees, and wasps, and even prey up to the size of tree frogs and hummingbirds. I and others suspect the reason we no longer see the smaller native Carolina Mantis in many areas is due to competition with this Asian introduction.
While making my photos, this hapless Cabbage White butterfly, Pieris rapae, dropped in and I knew it was toast. Camera at the ready, I managed some photos of the kill. Death by mantis is not a particularly pleasant way to go. First, you're crushed in a viselike grip by spined legs, then the mantis begins methodically consuming your body, usually starting with the head. Insofar as I know, no sedating neurotoxins or anything else that can take the edge off this experience are injected - this is pure unadultered raw carnivory.
If only the Chinese Mantids would stick to other nonnative creatures such as this butterfly, most people would probably not have many problems with them. In fact, we'd probably applaud them and hail the release of mantids as a good thing - an all too rare case of an intentional "biological control" introduction that worked. But they don't, and as a consequence mantis predation is just one more threat that many of our declining species of pollinating animals face.