Lycorma delicatula, a beautiful but destructive invader from China. Above we see the adult version; below are three views of the nymph in its late stage (an earlier stage looks similar, but black instead of red).
Allegheny County is in the Spotted Lanternfly quarantine zone, where these pests have become a serious problem. Their favorite host is the Tree of Heaven, otherwise known as Pittsburgh Palm or Tree from Hell (Ailanthus altissima), which is itself a beautiful but destructive invader from China. Spotted Lanternflies were unknown in the United States until 2014; now they are all over Pittsburgh. Although old Pa Pitt is inclined to say they can have as many Pittsburgh Palms as they want, these critters also cause damage to many other trees and vines. If you see one, you know what to do.
Here’s more about the Spotted Lanternfly from the Pennsylvania Department of Agriculture.