Old World Swallowtail
Papilio machaon
Overview
It has pale yellow wings with grey-black patterning on the forewings, and blue-black accents as well as red eyespots on the hindwings. The hindwings also have an extended ‘tail’, for which they are named swallowtail. The caterpillar is plump and pale green with black and orange markings on each body segment. The chrysalises vary in colour from green to brown with lighter camouflage markings.
There is no sexual dimorphism in size and appearance in the Old World swallowtail, and its average wingspan is 6.5cm to 8.6cm.
- Found in
- Europe, Asia, North America
- Class
- Insecta
- Order
- Lepidoptera
- Family
- Papilionidae
- Genus
- Papilio
Conservation Status
The Old World swallowtail is considered a species of Least Concern, although populations are becoming scarcer in some regions. It is affected by loss of habitat, water pollution and climate change. All butterflies are collected to some extent, but there is no trade information of concern for this species.
This species regularly occurs in protected areas across its range. Local declines should be addressed by protecting important habitats, especially wet fenland breeding sites, and monitoring population levels over time.
The long-term outlook for the Old World swallowtail is positive, and its overall population is considered to be increasing.
- Wild Population
- Unknown
- Conservation Status
- Least concern
Animal Facts
- The Old World swallowtail is the largest species of butterfly found in the UK.
- The Old World swallowtail caterpillar has an orange organ, called an osmeterium, on its head which protrudes and produces foul odours when threatened to scare off predators.
- The Old World swallowtail caterpillar is parasitised by a wasp species called Trogus lapidator that lays its eggs inside the body cavity of the caterpillar and feeds on it while it pupates, with the adult wasp emerging from the chrysalis.
- The tongue of the Old World swallowtail is adapted to feed on flowers with many small, thin, tubular petals such as dandelions.
- The Old World swallowtail is a fast, direct flier in comparison to many other species of butterflies.
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Social & Reproduction
Like most butterflies, the Old World swallowtail has no social needs outside of mating or competing for mates, but equally does tolerate conspecifics in its vicinity given access to enough resources.
Mating season occurs mid-summer between June and July. Old World swallowtail males engage in ‘hilltopping’ mating behaviour, attempting to defend a territory at the highest point of a hill. Males that maintain a territory at a high elevation are more likely to mate, as females will also fly to the highest points of terrain to mate. When a female selects a mate, she and the male will cling to the stem of a plant, face away from each other, and connect the tips of their abdomens.
Soon after mating, she lays her eggs one by one, one per leaf. In total, she may lay 200 to 430 eggs within 4 days. 4 to 10 days after laying, the caterpillars hatch from the eggs. They feed on the soft, young leaves of food plants like carrots and fennel for 3 to 4 weeks and then spin a chrysalis.
After pupating in the chrysalis for a period of 10 to 20 days, they emerge as adult butterflies. However, if they pupated towards the end of summer, they may remain in the chrysalis until the following year, when temperatures rise again. Depending on the time of year, hatched adults either hibernate or immediately look for a mate. Old World swallowtails die a week or two after mating, so those who hibernate before may live for roughly 9 months.