Based on 4,454 research-grade iNaturalist observations in Pennsylvania, Black Swallowtail is most often recorded in August; in Pennsylvania it behaves like a summer visitor / breeder. It ranks #7 among butterflies recorded in the state in our data.
Papilio polyxenes
Black Swallowtail in Pennsylvania by month
Bars show research-grade observations per month. They mix true seasonality with how often people are outdoors, so treat small numbers with caution.
Also seen in Pennsylvania in August
Monarch
Eastern Tiger Swallowtail
Zabulon Skipper
Silver-spotted Skipper
Spicebush Swallowtail
Huron Skipper
Pearl Crescent
Peck's Skipper
Places to look in Pennsylvania
National ForestAllegheny National Forest
State ParkPresque Isle State Park
Botanical GardenJenkins Arboretum
State ParkCherry Springs State Park
State ParkColton Point State Park
State ParkLeonard Harrison State Park
FAQ
When does Black Swallowtail appear in Pennsylvania?
Mainly June–September, with the most records in August.
How common is Black Swallowtail in Pennsylvania?
It ranks #7 by number of iNaturalist observations among butterflies in Pennsylvania (4,454 records in our sample).