- Name also: Common Yellow Swallowtail, Old World Swallowtail
- Family: Swallowtail Butterflies – Papilionidae
- Subfamily: Swallowtails – Papilioninae
- Wing span: Very large, 65–95 mm (2.56–3.74 in.). One of Finland’s largest butterflies. Females larger than males.
- Wing upper side: Yellow, leading edge of forewing with black patches. Margin of hind wing with row of blue blotches and one red blotch.
- Wing underside: Like upper surface.
- Habitat: All kinds of open environments, gardens, meadows, roadsides, logging sites and bogs.
- Flying time: Late May–early July. Second generation possible in late summer.
- Overwintering form: Cocoon.
- Larval foodplant: Carrot family (Apiaceae) such as wild angelica (Angelica sylvestris), garden angelica (A. archangelica) and milk-parsley (Peucedanum palustre).
The four species that belong to the Swallowtail family (Papilionidae) that can be found in Finland belong to two different subfamilies. The name subfamily Swallowtails (Papilioninae) is home to the swallowtail and the scarce swallowtail which, as the name suggests, is very rare. The other subfamily is the Snow Apollos (Parnassiinae).
The swallowtail can be found in all of Finland, especially the south-east of the country. It has long spurs on its hind wings which are helpful in making a definite classification as only scarce swallowtail has the same kind of (even longer) spurs. The leading edge of its forewings have black blotches and it lacks scarce swallowtail’s tiger stripes.
Swallowtails are often found alone. They fly quickly in straight lines and often over long distances. Males stake out their territory at the top of hills and sometimes in tree-tops, where they wait for females to arrive. The females lay their eggs one by one on the leaves of the host plant, and the lucky gardener might find the black and green caterpillars in among the carrots and dill. The caterpillars make their cocoons in August.