A New Butterfly Appears--Then Disappears

This summer (wet season) has seen many changes. The Great Barrier Reef seems to be dying, floods have hit parts of Australia that are normally dry and the so-called "Wet Tropics" seem to be drier than normal.

Along with that a different butterfly has appeared on the scene. The Tawny Coster, Acraea terpsicore, Nymphalidae has become part of the local scene--at least for a time.

This butterfly was first reported in Australia near Darwin in 2012. Since that time it has spread to the Kimberleys and is now well established on the opposite side of the continent near Kowanyama, Queensland. Last year one was seen near Georgetown, Qld and this year, in February, it was found at Talaroo, near Mt Surprise, Qld. Yours truly observed a few not far from Lake Mitchell on the Toll Road in February.

The Tawny Costa, Acraea terpsicore. (B Richardson photo)

About 3 weeks ago I observed large numbers of the butterfly while sitting at traffic lights on Sheridan St, Cairns, Qld. I saw 5 at one intersection in three minutes This butterfly is easily recognised on the wing. It flies slowly much in the manner of the Monarch Butterfly which does not occur here but is naturalised in temperate parts of Australia. The Tawny Coster is much smaller but from a distance appears similarly marked. I have not seen them at my place in Kuranda but understand they have been seen in the centre of town which is more open than here in the rainforest. 

For about three weeks I have not seen a single individual. They seem to have disappeared as promptly as they showed up here a month or so ago.

So where did this butterfly come from and how did it get to Australia. The Tawny Coster occurs naturally in India and Sri-Lanka but it has expanded its range to include Indonesia at the rate of 200 km per year (Braby et al., 2014a). The authors further report that the expansion in Australia is even more rapid at some 315 km per year (Braby et al. 2014b). 

The Tawny Coster is now established in Australia. It's host plant is Lilac-Spade Flower, Hybanthus enneaspermus.  The butterfly may be able to adapt to other plants which will enhance its ability to broaden its range. It and its caterpillars have been found at Talaroo, near Mt Surprise, Queensland, see Franklin et al., 2017.

The presence of the Tawny Coster in Australia is most likely a natural expansion of a species. Its ability to move around may have been enhanced by forest clearing in SE Asia but it may also be enhanced by Global Climate Change, a phenomenon that is being verified by many examples such as this. 

This recent discovery is documented in Franklin et al 2017.

Literature

Braby MF, Bertelsmeier C, Sanderson C, Thistleton BM. 2014a. Spatial distribution and range expansion of the Tawny Coster butterfly, Acraea terpsicore (Linnaeus, 1758) (Lepidoptera: Nymphalidae), in South-East Asia and Australia. Insect Conservation and Diversity 7: 132-143. 

Braby MF, Thistleton BM, Neal MJ. 2014b. Host plants, biology and distribution of Acraea terpsicore (Linnaeus, 1758) (Lepidoptera: Nymphalidae): a new butterfly for northern Australia with potential invasive status. Austral Entomology 53: 288-297. 

Franklin, DC, Morrison, SC, Wilson, G, 2017. Acolourful new Australian reaches Talaroo: The Tawny Coster, Acraea terpsicore. North Queensland Naturalist, 47: 10-13. 

http://media.wix.com/ugd/eb4488_95c868d0d9b542f69e5931ba4e34ba74.pdf