Citrus Swallowtail

EASY GARDEN BUTTERFLIES

Citrus SwallowtailPapilio demodocus demodocus

The Citrus Swallowtail is one of the Papilionidae (Swallowtails and Swordtails). Although it’s called a ‘Swallowtail’ its hindwings lack the long tails that its relatives have.

Citrus Swallowtail is a large and conspicuous butterfly with a powerful flight and the restless nature typical of Swallowtails. Males (wingspan 100-120mm) patrol large territories looking for females and food sources. They are often found congregating on wet sand and mud around water sources.

Females (wingspan 110-130mm) are found on flowers and close to their host plants. The sexes are similar; females have an orange tint to the cream ring around a large eyespot at the upper corner of the hindwing (not visible here).

Citrus Swallowtail is active from spring to autumn but it often peaks in midsummer. This is the reason for its other name, Christmas Butterfly.

Distribution

Citrus Swallowtail occurs throughout South Africa and is common almost everywhere except remote arid areas with little human habitation. Because it uses the popular cultivated Citrus as a caterpillar host plant it is found in areas where its wild host plants are absent.

Outside South Africa it’s found all over sub-Saharan Africa, the moister parts of the Arabian peninsula, Madagascar and the Indian Ocean islands.

Egg

Citrus Swallowtail eggs are typical of the family Papilionidae: tiny pearl-like spheres with flattened bases. They are white when laid, changing colour to pale yellow if fertile and then becoming green with faint brown mottling. They are 1.3mm high by 1.3mm diameter.

They are laid on the young shoots and leaves of the host plant, held in place by an adhesive secreted by the mother. The egg stage lasts about five days.

Young caterpillar

Young Citrus Swallowtail caterpillars are banded in black, white and yellow, and resemble bird droppings. When freshly hatched from the egg they are about 3mm long.

This camouflage gives them protection against predators like birds, which would not recognise them as a source of nutrition.

They have two rows of short spines along the body with forward-pointing ones behind the head. The tail is forked and also carries short spines.

The caterpillars take about 24-30 days to reach full size, undergoing four moults.

Mature caterpillar

Fully-grown Citrus Swallowtail caterpillars are green with pale grey underparts and irregular stripes of mottled grey. The effect is that of a partly eaten leaf with dry, dead patches.

If disturbed, all stages of this caterpillar will rear up and extrude a forked orange organ called an osmeterium. This emits a strong scent of oils from the host plant. Together with the eyespots on the thorax of a mature larva gives the impression of a small snake, which can startle away small predators.

Not all Citrus Swallowtail caterpillars feed on the Citrus family of plants. Some, like this one, use Apiaceae (Umbellifers) and their colouring affords them camouflage when feeding on these plants.

The final instar caterpillar takes about a week to ten days to reach a size of 35-45mm.

Pupa/Chrysalis

Citrus Swallowtail pupae are attached to leaves or stems of the plant by a tail hook and a silken girdle spun over their ‘waist’. They hang from the girdle as shown here.

They are variable in colour from bark-like grey to leaf green depending on the surface they are formed on. Many have patches of green and grey.

The pupa is about 35-38mm long. The pupal stage lasts from two weeks to several months when the insect undergoes diapause as a pupa.

Host plants

Citrus Swallowtail caterpillars feed on plants in the Rutaceae (Rue and Citrus) family, which often grow in gardens. They also use Apiaceae (Umbellifers) like Fennel Foeniculum vulgare. Wild South African Apiaceae like Deverra or Peucedanum species are skin irritants and don’t make good garden subjects. There are many local Rutaceae that this butterfly uses in the wild. Examples are White-ironwood, Vepris lanceolata, Horsewood Clausena anisata, Small knobwood Zanthoxylum capense, and Cape-chestnut, Calodendrum capense.

How to attract them

Gardeners can promote the presence of this butterfly by simply growing a Lemon tree! Some people don’t like the way the caterpillars eat holes in the leaves, although they seldom arrive in sufficient numbers to do real damage. One way to divert their attention from the Lemon tree is by cultivating its preferred wild host plants. An advantage of doing this is that other Swallowtail species, if present, will lay eggs on them and breed in the garden.

Like most butterflies they welcome open sunny areas with lots of flowers to visit for nectar. Swallowtails are particularly fond of large pink or red flowers like Hibiscus or Cape-honeysuckle.