Swallowtail

Overview

Papilio machaon, commonly known as the Old World Swallowtail or simply Swallowtail, is one of the most widespread and recognizable butterfly species in the Northern Hemisphere. It belongs to the family Papilionidae, which includes the largest and most colorful butterflies. The species exhibits considerable geographic variation across its vast range, with numerous subspecies recognized throughout Europe, temperate Asia, and parts of North America. This butterfly is characterized by its impressive wingspan and elegant flight pattern. The wings are predominantly yellow with black veining creating a stained-glass window effect. The hindwings feature distinctive tail-like projections, prominent blue scaling, and red eyespots that likely serve to deflect predator attacks away from vital body parts. These features make it one of the most photographed and admired butterflies in its range. The Swallowtail occupies diverse habitats from lowland meadows to mountain slopes, demonstrating remarkable ecological adaptability. It has been a subject of extensive scientific study regarding migration, host plant relationships, and population dynamics. In many regions, it serves as an indicator species for healthy, biodiverse grassland ecosystems.

How to identify

Adult Swallowtails have a wingspan of 65-86 mm (2.6-3.4 inches). The wings are bright yellow with thick black veins and black margins. The hindwings feature characteristic tail-like extensions (approximately 10 mm long), blue crescent-shaped markings along the outer margin, and a distinctive orange-red eyespot with a black center near the tail. The body is black with yellow markings. Males and females are similar in appearance, though females are typically slightly larger. In flight, they display a characteristic gliding and flapping pattern with wings held relatively flat.

Habitat

Papilio machaon inhabits open, flowery habitats including meadows, grasslands, marshes, alpine pastures, and cultivated areas such as gardens and agricultural edges. It prefers areas with abundant nectar sources and host plants for caterpillars. The species occurs from sea level to elevations above 2000 meters in mountainous regions. It favors warm, sunny locations with shelter from strong winds.

Distribution

The Swallowtail has one of the widest distributions of any butterfly species, ranging across temperate and subarctic regions of the Northern Hemisphere. In Europe, it occurs from the British Isles (very local in England) eastward across continental Europe. Its range extends through temperate Asia to Japan and into northern Africa (North Africa mountains). In North America, it is found in Alaska and Canada, with isolated populations in the western United States. The species is absent from tropical regions.

Diet

Adult Swallowtails feed on nectar from a wide variety of flowering plants, showing particular preference for purple and pink flowers such as thistles, knapweeds, scabious, and clover. Caterpillars are specialist feeders on plants in the carrot family (Apiaceae), including wild carrot, fennel, milk-parsley, hogweed, and cultivated herbs like parsley and dill. The larvae also feed on Rutaceae in some regions. Young caterpillars consume leaves, while older instars can strip entire plant stems.

Behavior

Swallowtails are strong, active fliers capable of covering considerable distances. Males exhibit hilltopping behavior, congregating on elevated terrain to locate females. They are also known to engage in puddling behavior, gathering at damp soil to extract minerals. Adults are most active during sunny, warm weather and tend to bask with wings spread to regulate body temperature. The species shows territorial behavior, with males patrolling specific areas. Flight is characterized by a distinctive gliding pattern interspersed with rapid wing beats.

Reproduction & life cycle

Papilio machaon typically produces one to three generations per year depending on latitude and climate (univoltine in northern regions, bivoltine or trivoltine in southern areas). Females lay spherical, pale yellow eggs singly on host plants. Eggs hatch after approximately one week. Caterpillars pass through five instars over 3-4 weeks, changing from black with white markings (early instars) to green with black bands and orange spots (final instar). When threatened, larvae evert a bright orange, fork-shaped osmeterium that releases a pungent defensive chemical. Pupation occurs on plant stems or nearby structures, with the chrysalis either green or brown depending on substrate. In colder regions, the species overwinters as a pupa. Adults typically live 2-4 weeks.

When to look

Adults fly from April to September in most of Europe (peak May-August), with earlier emergence in southern regions and later in northern areas. Single generation appears June-July in northern regions; multiple generations occur April-September in warmer climates. Overwinters as chrysalis in temperate zones.

Cultural significance

The Swallowtail has held symbolic importance in many cultures, often representing transformation, beauty, and the ephemeral nature of life. In Britain, where it is rare and restricted to the Norfolk Broads, it is an iconic conservation flagship species and appears on conservation organization logos. The butterfly has been featured on postage stamps of numerous countries and is a popular subject for artists and photographers. In some regions, sighting a Swallowtail is considered a sign of good fortune. It has also contributed to scientific understanding of mimicry, as its caterpillar resembles bird droppings in early instars.

Similar species

• Papilio hospiton (Corsican Swallowtail)
• Papilio zelicaon (Anise Swallowtail)
• Iphiclides podalirius (Scarce Swallowtail)

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