Butterfly of the Month - October 2021

Orchard Swallowtail (Papilio aegeus)

The Orchard Swallowtail is one of Brisbane's largest butterflies.. Many of you will have encountered this beauty and will easily recognise it. You can't miss it just by its size. According to M. F. Braby the size varies from a wingspan of 102mm (male, below right) to 108mm (female, below left), some describe them as larger. The males are predominantly black with white markings while the female is very attractive with extensive white-greyish markings and additional red and blue ones on the hindwing.

Once emerged from the egg, the caterpillar (larva) looks like a bird dropping, brown and white in colour, with growth gradually altering its appearance through instar stages to a mostly green colour before it changes into the pupa (chrysalis). The chrysalis may adapt its colour too depending on where it is positioned, presumably to blend into the surrounds. 

This butterfly has many larval hosts. Home gardeners will find its caterpillars on citrus trees and the adult butterfly on many flowering garden plants. Among the native host plants for larvae are Lime berry (Micromelum minutum), native limes (Citrus australis, C. australasica), and Crow's Ash (Flindersia australis). 

Did you know that this butterfly's larva (like that of other swallowtails) uses a red osmeterium to warn predators? Osmeteria look like a little forks and are located just behind the caterpillar's head. They are everted when the larvae feel threatened.