Western Tiger Swallowtail
A big yellow swallowtail patrols Black Hills streams and canyon edges, often descending to damp mineral-rich ground.
Artwork inspired by Grace French
Females place eggs on willows, cottonwoods, aspen, and related host trees. Caterpillars begin bird-dropping brown and become green with eyespots, while adults gather salts at puddles and patrol long linear territories.
Do not crowd a puddling group; photograph upper and lower wing surfaces because eastern and Canadian tiger swallowtails can complicate identification near range boundaries. Stay long enough to see normal behavior, but not so close that Western Tiger Swallowtail retreats or stops feeding.
- Best clue
- Large yellow butterfly with four black tiger stripes and tail-like hindwing extensions
- Habitat
- wooded streams, canyon roads, parks, and forest edges
- Regional status
- Native regional species
Quick guide
- First read
- Four black tiger stripes
- Second evidence
- Stream-canyon patrols
Separate Western Tiger Swallowtail from a quick look-alike
- Start with structure
- Let the whole form of Western Tiger Swallowtail lead.
- Look beyond silhouette
- Compare long hindwing tails with the nearest plausible look-alike, paying particular attention to yellow upperwings.
- Put the sighting in place
- Expect the strongest context in wooded streams, canyon roads, parks, and forest edges.
- Finish lightly
- Let Western Tiger Swallowtail settle naturally; netting, chilling, baiting, or repositioning weakens the observation.
Good to know
The caterpillar begins life resembling a bird dropping, then becomes green with large false eyespots—a two-stage disguise produced by growth rather than two species.
Notice these
- Four black tiger stripes
- Long hindwing tails
- Yellow upperwings
- Stream-canyon patrols