Papilio machaon oregonius

Distinguished from other North American swallowtails by the combination of yellow and black banding with hindwing tails, and from other P. machaon subspecies primarily by geographic location. Overlaps with P. zelicaon (Anise Swallowtail) in parts of its range; P. machaon oregonius has more extensive yellow on the forewing and different banding pattern. The subspecies P. m. hippocrates (found in Alaska and Yukon) differs in having more extensive blue markings. Genitalia examination may be required for definitive identification of some specimens.

Adults display the characteristic yellow and black banded pattern of Papilio machaon, with tails on the hindwings. The Oregon subspecies typically shows reduced blue and red spotting on the hindwings compared to European populations. Wingspan ranges approximately 50-70 mm. Larvae are green with black bands and orange spots, featuring the retractable osmeterium (scent gland) typical of papilionid caterpillars. Early instar larvae resemble bird droppings, a common defensive mimicry in Papilio species.

Occurs in open habitats including meadows, riparian areas, and disturbed sites where larval host plants grow. Associated with moist valleys, stream banks, and agricultural areas in the Pacific Northwest. Elevation range extends from lowlands to moderate elevations in mountainous regions.

Endemic to the Pacific Northwest of North America, including Oregon, Washington, and adjacent parts of Idaho and British Columbia. The subspecific range is bounded by the Cascade Range and extends eastward into the interior basins.

Adults are active from late spring through summer, with peak flight typically occurring June to August. Multiple broods may occur in favorable years, with the number of generations varying by latitude and elevation.

Larvae feed on plants in the Apiaceae (carrot family), including species of Lomatium, Perideridia, and cultivated parsley and carrot. Adults nectar at a variety of flowers including thistles, milkweeds, and composites.

• Lomatium - larval foodplantNative umbelliferous plants
• Perideridia - larval foodplantNative umbelliferous plants
• Daucus carota - larval foodplantWild carrot, introduced host
• Petroselinum crispum - larval foodplantCultivated parsley

Eggs are deposited singly on host plant leaves. Larvae pass through five instars, with early instars exhibiting bird-dropping mimicry and later instars displaying eyespot patterns and eversible osmeterium for defense. Pupation occurs on host plants or nearby vegetation, with the chrysalis resembling a twig or dead leaf. Overwintering occurs as pupa in most of the range. Development time varies with temperature; complete generation may occur in 6-8 weeks under favorable conditions.

Adults engage in hilltopping behavior for mate location, with males patrolling ridge tops and summits. Both sexes visit mud puddles and moist ground for mineral uptake. Flight is strong and direct, with adults capable of sustained gliding. Males exhibit territorial behavior at hilltop sites. Larvae display thanatosis (playing dead) when disturbed, in addition to osmeterium eversion.

Adults function as pollinators for diverse flowering plants. Larvae serve as herbivores, consuming plant biomass and transferring nutrients to higher trophic levels. The species participates in mimicry complexes and serves as prey for birds, parasitoid wasps, and other insectivores. Population fluctuations may indicate habitat quality changes in riparian and meadow ecosystems.

Subject to butterfly collecting and observation. Occasionally considered a minor agricultural pest when larvae feed on cultivated parsley, carrot, or dill. Featured in regional conservation assessments due to habitat loss in the Willamette Valley and other parts of its range. Not listed under federal or most state endangered species statutes, though local populations may be threatened by development and agricultural intensification.

• Papilio zelicaonOverlaps in range and shares similar size and general appearance; differs in forewing pattern with P. zelicaon having more black and less yellow on forewing, and lacking the complete yellow band characteristic of P. machaon
• Papilio polyxenesSmaller black swallowtail with reduced yellow markings; no hindwing tails in most populations, and different larval host plant preferences
• Papilio machaon hippocratesAnother North American subspecies of P. machaon found in Alaska and Yukon; differs in more extensive blue and red spotting on hindwings

• Papilionidae
• swallowtail
• Pacific Northwest
• Apiaceae feeder
• hilltopping

• BugGuide
• NCBI Taxonomy
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