Butterfly of the Month - August 2024

The Monarch or Wanderer (Danaus plexippus) is one of the most recognised butterflies in Australia, yet it originates from the North American continent where it is known for its spectacular migration. The butterfly wasn't introduced to Australia, it found its own way to our continent and was first recorded in SE Qld in 1871.

The Monarch starts its life cycle as a tiny egg, between 0.8mm and 1.2mm in size, somewhat conical in shape with a pointed top and vertical ribs. White in colour at first, it changes to a pale yellow. Eggs are laid singly on the underside of leaves, sometimes on young shoots and even flower buds. 

Larvae are easily recognised with their black, yellow and white bands as well as the fleshy black filaments protruding from the thorax. 

The Monarch's pupae are attached to the host plant and also often to a nearby object. Their appearance is of a very light green at the beginning, turning darker when the pupal case hardens. The pupa is adorned with tiny golden spots. Our image also shows the very late stage just before eclosing, with the wing pattern already shining through.

The introduced Red-head Cotton Bush (Asclepias curassavica) and Balloon Cotton Bush (Gomphocarpus physocarpus and G. fruticosus), all seemingly existing in abundance, allow for the butterfly to thrive. While larvae are often attacked by parasitic Tachinid flies, also happening to immature stages of other butterflies, they are not eaten by birds because of their toxic contents derived from the host plants which are milkweed plants from the Dogbane family (Apocynaceae). Monarch (Danaus plexippus), Dabbage White (Pieris rapae) and Tawny Coster (Acraea terpsicore) are the three butterflies not originating in Australia. All are now widespread and here to stay.

Images: CM - Cliff Meyer, GO - Greyson Orlando, CC BY-SA 3.0; PC - Peter Chew