Papilio machaon

Distinguished from the sympatric Corsican and Sardinian species Papilio hospiton by longer hindwing tails. Separated from the Algerian Papilio saharae only by antennal segment count. The British subspecies P. m. britannicus is darker and more heavily marked than continental European populations. The combination of yellow wings with black veining, paired hindwing tails, and the characteristic eyespot pattern (one red, six blue) is diagnostic within most of its range.

Occurs in diverse habitats from sea level to 4,900 m elevation. In Fennoscandia, primarily inhabits predictable formations of inland wetlands and coastal foreshores. At lower elevations, frequents alpine meadows, hillsides, and gardens where host plants occur. Males engage in hilltopping behavior, congregating near summits. The British subspecies is restricted to fenland habitats in the Norfolk Broads. In the Himalayas, found from 610 m in Kashmir valley to 4,900 m in Garhwal, with lower elevation limits in Himachal Pradesh (1,200 m+) and Sikkim (2,400 m+).

Widespread across the Palearctic from Russia through China, Japan, Taiwan, and the Himalayas. Extends into North America (Alaska, Canada, United States). Present throughout Europe; in southern Asia recorded from Saudi Arabia, Oman, Yemen, Lebanon, Iran, Israel, Pakistan, Kashmir, northern India, Nepal, Bhutan, and northern Myanmar. Recently documented in Punjab, India at 293 m elevation. In the United Kingdom, restricted to Norfolk Broads of East Anglia.

Flight period varies by elevation and latitude. At lower elevations, adults fly from March to September. At higher elevations, activity is constrained by short summer seasons. In northern areas, the species may be univoltine; elsewhere two to three broods occur annually. Some populations exhibit partial bivoltinism with individuals either pupating and emerging the same year or overwintering as pupae.

Adults feed on nectar from flowering herbs. Larvae feed primarily on plants in the family Apiaceae (Umbelliferae). Documented host plants include Peucedanum palustre (milk parsley, primary foodplant for British subspecies), Angelica archangelica, Angelica sylvestris, Daucus carota (wild carrot), Foeniculum vulgare (fennel), Heracleum (hogweeds), Petroselinum crispum (parsley), Anethum graveolens (dill), Pastinaca sativa, and Aegopodium podagraria. In Malta, larvae also feed on Ruta chalepensis (Rutaceae). Laboratory studies indicate host plant suitability hierarchy: Peucedanum > Angelica > Pastinaca > Aegopodium.

• Peucedanum palustre - primary larval foodplantMilk parsley; sole foodplant for British subspecies P. m. britannicus in natural habitats
• Angelica archangelica - larval foodplantParticularly subspecies littoralis and norvegica in Fennoscandia
• Angelica sylvestris - larval foodplantWild angelica; common host in Europe
• Foeniculum vulgare - larval foodplantFennel; frequently used in gardens and cultivation
• Anethum graveolens - larval foodplantDill; observed in Punjab, India and used in cultivation
• Ruta chalepensis - larval foodplantRue; used in Malta alongside umbellifers

Eggs laid singly on young host plant sprouts. Caterpillar passes through five instars; early instars with bird-dropping camouflage, later instars green with black and orange markings. Pupation occurs on available structures after silken attachment. Development time temperature-dependent: 1–2 weeks in warm summer conditions, several months at lower temperatures. Overwintering occurs as pupa. Generation number varies geographically: univoltine in northern areas, bivoltine to trivoltine elsewhere; partial bivoltinism observed in some populations.

Strong, fast flight with frequent hovering at flowers to nectar. Males exhibit hilltopping, congregating at summits to locate females. Females oviposit singly on host plants, with preferences influenced by rearing experience—newly hatched larvae show no discrimination among suitable hosts, while third-instar larvae prefer the species on which they were reared. The British subspecies P. m. britannicus is less mobile than continental forms and remains near fenland habitat.

Larval herbivore on Apiaceae; adult pollinator. Serves as host for parasitoid wasp Trogus lapidator (Ichneumonidae), which emerges from P. machaon pupae.

Culturally significant as the National Butterfly of Estonia (selected 2017, declared 2018). Subject of conservation concern in Britain, Austria, South Korea, and parts of former Soviet Union; protected by law in UK, India (subspecies verityi), and several European countries including Austria, Czech Republic, Slovakia, Hungary, Romania, and Moldova. Easily bred in captivity for education and conservation. Larval frass metabolites show potential pharmaceutical activity against HCT116 colon cancer cells when reared on Angelica keiskei.

• Papilio hospitonOccurs sympatrically on Corsica and Sardinia; distinguished by shorter hindwing tails
• Papilio saharaeAlgerian species; distinguished only by antennal segment count
• Papilio xuthusAsian species; hybridization with P. machaon hippocrates produces viable F1 offspring with intermediate flight and behavioral characteristics

• butterfly
• swallowtail
• Apiaceae feeder
• widespread
• hilltopping
• osmeterium defense
• fenland specialist Britain
• pharmaceutical potential

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Provisional checklist of European butterfly larval foodplants
• The ecology and conservation of Papilio machaon in Britain
• Studies of Various Behavior Patterns in the Hybrid between Papilio xuthus LINNE and Papilio machaon hippocrates C. et R. FELDER (Lepidoptera : Papilionidae)
• The evolutionary relationship between adult oviposition preferences and larval host plant range in Papilio machaon L.
• Generalist vs. Specialist Oviposition Behaviour in Papilio Machaon (Lepidoptera) and Functional Aspects on the Hierarchy of Oviposition Preferences
• Figure 1–10 from: Shaw MR, Kan P, Kan-van Limburg Stirum B (2015) Emergence behaviour of adult Trogus lapidator (Fabricius) (Hymenoptera, Ichneumonidae, Ichneumoninae, Heresiarchini) from pupa of its host Papilio machaon L. (Lepidoptera, Papilionidae), with a comparative overview of emergence of Ichneumonidae from Lepidoptera pupae in Europe. Journal of Hymenoptera Research 47: 65-85. https://doi.org/10.3897/JHR.47.6508
• Range Expansion of Papilio machaon (Linnaeus, 1758) (Lepidoptera: Papilionidae) in Punjab, India
• The Concept of Oligophagy and the Natural Habitats and Host Plants of Papilio machaon L. in Fennoscandia
• The effect of host plant on larval survivorship of the Alaskan swallowtail butterfly (Papilio machaon aliaska)
• MITOCHONDRIAL DNA PHYLOGENY OF THEPAPILIO MACHAONSPECIES GROUP (LEPIDOPTERA: PAPILIONIDAE)
• HOST PLANT SUITABILITY AND THE MECHANISM OF HOST SELECTION IN LARVAE OF PAPILIO MACHAON
• An extract from the frass of swallowtail butterfly (Papilio machaon) larvae inhibits HCT116 colon cancer cell proliferation but not other cancer cell types