Butterfly dossiers › Swallowtails › Old World Swallowtail
Old World Swallowtail
Papilio machaon · Swallowtails
The Old World swallowtail is the swallowtail of European meadows, alpine passes and Siberian steppe. It is intensely yellow - brighter than any American swallowtail - marbled with black and finished with a red and blue eyespot on the hindwing. In the lowlands it is now largely a butterfly of wild places, but it still turns up on fennel and rue in country gardens.
- 6.5-8.6 cm wingspan
- Swallowtails
- Host: Wild carrot, fennel, milk parsley, dill, rue
Identification
The easiest field mark is the hindwing eyespot: a red patch centred on black, ringed with blue scales, sitting in the angle between the tail and the inner margin. Two black bands cross the yellow forewing, and the veins are black and crisp. Compared with the scarce swallowtail, which shares much of its range, the Old World swallowtail has tails and a red eyespot; the scarce swallowtail is cream with long tiger stripes and no tails.
Habitat and where to look
Dry flower-rich grassland, alpine meadows, rocky slopes, coastal dunes and marshy fens where milk parsley grows. It is a strong flier and can be found hill-topping on ridges in the afternoon. In mountain regions it follows the flowering season upward, appearing at 2,000 m and above in July and August where lowland populations are already finished.
Life cycle
Eggs are laid on the flower heads of the host, one per head, so the caterpillar starts life surrounded by food. The caterpillar is lime green with black cross-bands and a ring of orange dots, and when disturbed it rears up and pushes out its osmeterium, which in this species is bright orange and strongly scented. The pupa is remarkable: in warm years it hatches in a fortnight, but in cold or dry conditions it can stay dormant for two or three winters before the adult emerges. This is one of the reasons the species can vanish from a site for years and then reappear.
How to attract it
Wild carrot and fennel are the two most useful host plants, and both are handsome enough for a front border. Rue is worth growing for the caterpillars even though it is toxic to mammals, including humans - wash your hands after handling it and keep it away from small children. For nectar, plant lavender in a broad band rather than as isolated bushes, and add field scabious for late summer. Because the adults hill-top, a garden on high ground will always see more of them than one in a valley.