Western Tiger Swallowtail (Papilio rutulus)
COMPARED TO Pale Swallowtail (Papilio eurymedon)
COMPARED TO Anise Swallowtail (Papilio zelicaon). All 3 are in the Swallowtails (Papilioninae) subfamily.

(Note: Taxonomic name changes occur regularly following DNA discoveries. Tenny's excellent butterflies field guide follows the 2022 update to the Pelham Catalogue for both scientific and common name changes. For example, old name for Western Tiger Swallowtail is Papilio rutulus, Tenny uses newer Pterourus rutulus.
Butterflies of Monterey County: A comprehensive guide to finding and identifying 91 species of butterflies in Monterey County, Chris Tenney and Jan Austin, August 2023, p. 15.)

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Western Tiger Swallowtail (Papilio rutulus a.k.a. Pterourus rutulus) is a large, native butterfly in the Swallowtails (Papilioninae) subfamily. Wing span is 2.75 - 3.5 inches. It is deeper yellow with narrower black stripes than Pale Swallowtail. It has 2-3 flights, March-October. It's a puddler and favors riparian canyons, city parks, and neighborhoods. Adult nectaring favorites include California Buckeye, Willows, Sycamore, Cottonwoods and garden landscaping.

Butterflies of Monterey County: A comprehensive guide to finding and identifying 91 species of butterflies in Monterey County, Chris Tenney and Jan Austin, August 2023, pp. 18-19. (Pterourus is the newer genus name used.)

Butterflies Through Binoculars: The West: a field guide to the butterflies of western North America, by Jeffrey Glassberg, 2001, pp. 50-51.

Link to closeup profile views of Western Tiger Swallowtail: https://www.inaturalist.org/observations/81632292 and https://www.inaturalist.org/observations/122248991 and top view: https://www.inaturalist.org/observations/128078719

Butterflies and Moths of North America https://www.butterfliesandmoths.org/species/Papilio-rutulus

BugGuide: https://bugguide.net/index.php?q=search&keys=Papilio+rutulus

Field Guide to California Insects, by Kip Will, J. Gross, D. Rubinoff , J. Powell, 2nd ed., 2020, pp. 424-426.

Kaufman Field Guide to Butterflies of North America. Brock and Kaufman, 2003, p. 22-23.

Butterflies & Their Favorite Flowering Plants: Anza-Borrego Desert State Park & Environs, Lynn and Gene Monroe, 2004, p. 22.

My favorite photo/observation:

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COMPARED TO

Pale Swallowtail (Papilio eurymedon a.k.a. Pterourus eurymedon) Large, native butterfly in the Swallowtails (Papilioninae) subfamily. Wing span is 2.75 - 3.5 inches. It is creamy-white to pale yellow. The black vertical stripes are broader than those of Western Tiger, and it tends to have more pointed forewings than Western Tiger, and the long tails have a half twist. Pale Swallowtail has one flight, March - July. it is often seen puddling for mineral nutrients in groups, with heads all facing in the same direction. Larval food plants include Coffeeberry, Alder, and Ceanothus. Adult nectaring favorites are Mints, Thistle, Yerba Santa, and California Buckeye.

Butterflies of Monterey County: A comprehensive guide to finding and identifying 91 species of butterflies in Monterey County, Chris Tenney and Jan Austin, August 2023, pp.20-21. (Pterourus is the newer genus name.)

Link to observation of large cluster of Puddling Pale Swallowtails: https://www.inaturalist.org/observations/165606552

Butterflies Through Binoculars: The West: a field guide to the butterflies of western North America, by Jeffrey Glassberg, 2001, pp. 50-51.

Butterflies and Moths of North America https://www.butterfliesandmoths.org/species/Papilio-eurymedon

BugGuide: https://bugguide.net/index.php?q=search&keys=Papilio+eurymedon

My favorite photo/observation:

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COMPARED TO

Anise Swallowtail (Papilio zelicaon) is a large, native butterfly in the Swallowtails (Papilioninae) subfamily. Wing span is 2.5 - 3 inches. It is smaller than Pale and Western Tiger Swallowtails. It has a black upper basal forewing with yellow bars, instead of alternating black and yellow tiger stripes. Yellow can vary from pale to deep yellow. Upper surface of hind wing has yellow-orange eyespot near tail with a round black center that is not connected to hindwing margin. Anal cell of hind wing is primarily yellow. It is a hilltopper. It is commonly seen on open, exposed hilltops. Larval food plants include native and introduced carrot family plants like fennel and poison hemlock. Thistles are favorite adult nectaring plants.

Butterflies of Monterey County: A comprehensive guide to finding and identifying 91 species of butterflies in Monterey County, Chris Tenney and Jan Austin, August 2023, pp. 16-17.

Butterflies Through Binoculars: The West: a field guide to the butterflies of western North America, by Jeffrey Glassberg, 2001, pp. 48-49.

Butterflies and Moths of North America https://www.butterfliesandmoths.org/species/Papilio-zelicaon

Field Guide to California Insects, by Kip Will, J. Gross, D. Rubinoff , J. Powell, 2nd ed., 2020, pp. 424-425.

My favorite photo/observation:

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Butterfly and Caterpillar (General References)

Field Guide to California Insects, by Kip Will, J. Gross, D. Rubinoff , J. Powell, 2nd ed., 2020 (Lepidoptera, pp. 347-426)

BugGuide: Butterflies and Moths (U.S. and Canada) clickable categories or use search bar: https://bugguide.net/node/view/57

Glossary of Butterfly (and Moth) Terminology: https://butterfly.ucdavis.edu/resources/glossary

Butterflies of Central and Northern California, a laminated pamphlet (guide to common and notable species) by Jim Brock,, 2023

Caterpillar Anatomy diagram and Butterfly Basics: https://www.enchantedlearning.com/subjects/butterfly/activities/printouts/caterpillarprintout.shtml Life Cycle of a Butterfly: Egg --> Larva (the caterpillar) --> Pupa (the chrysalis or cocoon) --> Adult.

Caterpillars: INaturalist Project https://www.inaturalist.org/projects/california-caterpillars

Wagner's Caterpillars of Western North America (coming soon) "1450+ species accounts in progress" INat thebals 6/6/23.

Butterflies of Monterey County (coming soon: Companion website to text): https://www.montereybutterflies.online/