Swallowtail

• Its caterpillar defends itself with an osmeterium, a forked gland that squirts a foul-smelling fluid.
• The caterpillar feeds on plants such as fennel, wild carrot and parsley.
• The adult sips nectar from a wide range of flowers.
• defensaIts caterpillars can push out a fleshy, foul-smelling structure (the osmeterium) from behind the head to fend off predators.
• The caterpillar has an osmeterium: a forked orange organ that it flicks out suddenly behind its head, like the horns of a slug, and which releases an acrid, repellent smell.
• It practises hilltopping: males gather on the tops of hills and mountains, where they defend prominent positions and wait for the females. It is an encounter strategy in low-density species, where searching for one another at random would be inefficient.
• The caterpillar changes appearance completely as it grows: young ones are black with a white band and imitate a bird dropping, while older ones are green with black bands and orange spots.
• The chrysalis is held to the stem by a silk girdle, and its colour depends on the substrate: green if it will not last long, brown if it is going to overwinter.
• It is one of the largest and most striking butterflies in Europe, and in the United Kingdom it is restricted to the wetlands of Norfolk.

Skeleton type

Invertebrate - chitin exoskeleton

Habitat & environment

Open meadows, gardens and herb-rich ground across Europe, Asia and North America (from the Arctic to Alaska)

Birth weight

A tiny spherical yellowish egg, laid singly on host plants

Size at birth

A tiny egg 1-2 mm across

Sexual maturity

The adult emerges already sexually mature and ready to breed

Gestation / incubation

1-2 weeks of egg development; 3-4 weeks as a caterpillar; 2-3 weeks as a chrysalis (or the whole winter if it overwinters at that stage)

Litter / clutch size

Eggs laid singly, in numbers that vary from female to female

Sources consulted: Swallowtail and Birdwing Butterfly Trust; Butterfly Boogie; Butterflies and Moths of North America; Plantiary; First Nature; Buy-Butterflies.com; Butterfly Identification