Butterfly of the Month - December 2021
Clearwing Swallowtail (Cressida cressida)
One of our large butterflies locally with a wingspan of 90mm (male) and 95mm (female) and of impressive beauty. While the female, not dissimilar to birds, tends to blend into the background with her light looks, the male exhibits more striking colours. Both have transparent forewings. While those of the female have more of a grease proof paper tint, the ones of the male butterfly are likely the reason why the butterfly is called ‘Clearwing Swallowtail’.
Like so many of their relatives in the butterfly world, the larvae have a very limited amount of food plants to choose from. In Brisbane the female seeks out Aristolochia meridionalis as well as Pararistolochia praevenosa. The first plant is a small leaved vine which can be found on the ground in open eucalypt forest meandering through grasses. Watch out for low flying females in search of plants to lay her eggs on. Pararistolochia praevenosa is much better known as the larval host for the Richmond Birdwing butterfly. This vine is much larger leaved and has its habitat in moister conditions doing well especially at the edge of our dry rainforests.
Unfortunately, the butterfly also lays eggs on the introduced Dutchman’s Pipe (Aristolochia elegans), a declared weed in Queensland and NSW. According to Brisbane City Council’s website the vine is “primarily a weed of rainforests, closed forests, urban bushland, disturbed sites, roadsides, waste areas, waterways and forest margins in tropical and sub-tropical regions”. While Clearwing Swallowtails are generally able to complete their lifecycle feeding on this plant, some may not survive.
Keep your eyes out for tiny eggs as well as larvae, depicted here at different instar stages. If you want to see this stunning butterfly, plant for it, or enjoy a walk through—for instance—habitat areas such as the slopes of Mt Coot-tha or Toohey Forest where Aristolochia meridionalis occurs naturally.
Images: PC-Peter Chew, Brisbane Insects; HMK-Hongming Kan, BOIC; JG-Jutta Godwin; RM-Robert(Bob) Miller, egg and caterpillars;