Based on 8,551 research-grade iNaturalist observations in California, Western Giant Swallowtail is most often recorded in September; in California it behaves like a summer visitor / breeder. It ranks #22 among butterflies recorded in the state in our data.
Heraclides rumiko
Western Giant Swallowtail in California 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 California in September
Monarch
Fiery Skipper
Gulf Fritillary
Gray Hairstreak
Woodland Skipper
Gray Buckeye
Small White
Umber Skipper
Places to look in California
Botanical GardenThe Huntington Library, Art Museum, and Botanical Gardens
State ParkHearst Castle
Botanical GardenSan Francisco Botanical Garden
State ParkAnza-Borrego Desert State Park
National ForestAngeles National Forest
National ForestSequoia National Forest
FAQ
When does Western Giant Swallowtail appear in California?
Mainly July–October, with the most records in September.
How common is Western Giant Swallowtail in California?
It ranks #22 by number of iNaturalist observations among butterflies in California (8,551 records in our sample).