They spotted an unusually large blob on their radar, which was not precipitation. They determined this is most likely a migration of insects including lanternflies and dragonflies in the Philadelphia area.
Philadelphia police tweeted a PSA to please not call 911 to report a lanternfly sighting.
Please do NOT call 911 to report #SpottedLanternfly sightings. While they are a nuisance, they are not a police issue. And on that note, we, for one, would like to welcome our new insect overlords. Maybe they would like to build some nests on our vast concrete headquarters? pic.twitter.com/PXmCs4db0f— Philadelphia Police (@PhillyPolice) September 12, 2019