Butterfly of the Month - March 2023
The Glasswing (Acraea andromacha) is a common butterfly in Brisbane. It has a wingspan of 53mm (male) or 56mm (female). It stands out because the forewings are transparent with very few dark markings whereas the hindwings are white, but their markings are more numerous, and they and the band edging the wings are dark brown to black in colour.
Superficially, the butterfly resembles our December 2021 Butterfly of the Month (Clearwing Swallowtail - Cressida cressida) by its size alone. When you compare both species, you will see wing pattern and colour differences.
Acraea andromacha starts its life as a bright yellow egg of just under 1mm in size. It changes its colour to a cream variation. Unlike that of many other butterflies, this egg is shaped ovate. It is adorned with longitudinal ridges. Eggs are laid in clusters which can be of over 100 in size. The emerging larvae continue the close company when feeding, but are solitary in later instar stages.
All instars of the larvae, light brown in colour, show a multitude of branched spines. You can see the shed skin of the last instar with all its spines still attached to the pupa in our image. This butterfly’s cream pupa is pretty with its black edges which golden markings. Pre emergence of the adult butterfly the pupa may take on a lightly salmon coloured appearance, in our image a little stronger than usual.
Adults fly low, only a few meters off the ground, the females in pursuit of host plants, the male in pursuit of females. After mating the male provides the female with a ‘chastity belt’ by attaching a hardening substance to the opening at the tip of the abdomen.
Passionflower vines such as Passiflora herbertiana and P. aurantia are among the common native larval host plants in Brisbane, as is Spade Flower (Hybanthus stellarioides). While miscellaneous exotice Passion vines are used as well, the commercial variety of Passionfruit in your garden is not on this butterfly’s menu.
Images: MV-Museum Victoria CC BY; PC-Peter Chew, Brisbane Insects; SA-Sylvia Alexander