Based on 7,194 research-grade iNaturalist observations in Illinois, Black Swallowtail is most often recorded in July; in Illinois it behaves like a summer visitor / breeder. It ranks #2 among butterflies recorded in the state in our data.
Papilio polyxenes
Black Swallowtail in Illinois 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 Illinois in July
Monarch
Red Admiral
Eastern Tiger Swallowtail
Silver-spotted Skipper
Pearl Crescent
Eastern Tailed-Blue
Common Buckeye
Small White
Places to look in Illinois
State ParkCahokia
Botanical GardenMorton Arboretum
National ForestShawnee National Forest
Botanical GardenChicago Botanic Garden
Botanical GardenLadd Arboretum
State ParkStarved Rock State Park
FAQ
When does Black Swallowtail appear in Illinois?
Mainly June–September, with the most records in July.
How common is Black Swallowtail in Illinois?
It ranks #2 by number of iNaturalist observations among butterflies in Illinois (7,194 records in our sample).