SOUTH AUSTRALIAN SUN-MOTHS


The sun-moths belong in the Castniidae Family, which in the Australian Region presently contains the single genus Synemon Doubleday, 1846. They are dayflying moths, small to medium in size with a wing expanse of 25-55 mm. The forewings are a cryptic brown or grey colour, but their hindwings usually contain bright red, orange or yellow colours that are used as a sudden flash-display mechanism.  They are often mistaken for butterflies and skippers, and even have clubbed antennae similar to butterflies, but the hindwings have a frenulum. They have a rudimentary proboscis and therefore do not feed on nectar, living off the stored fat tissue accumulated during the larva-pupa stage.  Consequently as museum specimens the moths often become greasy looking.

The moths are restricted to the temperate and tropical habitat areas of mainland Australia, but are absent from the very arid inland areas and on Tasmania. They fly rapidly in sunshine, close to the ground.  The moths rest on the ground or on grasses and low plants, with the forewings covering the hindwings.  In warm conditions resting moths are very timid and can be very difficult to approach. They inhabit grasslands and low sedge-rush lands or very open woodlands that contain their hostplants in the understorey. Their habitat has suffered drastic fragmentation and alteration due to agriculturalisation, pastoralisation and urbanisation, and many species are threatened. Flight times are mainly univoltine during spring and summer, but some species fly like S. selene fly during autumn. 

Eggs are elongate with longitudinal ridges. The female is usually endowed with a long tubular spine-like ovipositor used to penetrate into the base of their hostplants to deposit the eggs in crevices near soil level.  The larvae feed on grasses, low tussock sedges and mat-rushes.  The larvae are of witchetty grub form and usually live at the base of the hostplant or tunnel underground to feed on roots.  This adapation would likely protect the larvae from the above ground effects of drought, dry conditions and infrequent fires, but has not protected them from the modern farming practices of tillage, overgrazing and trampling by stock, use of broad-acre insecticides and herbicides, and frequent fires. Pupation either occurs within the base of the hostplant or in the soil at the end of a silk-lined tunnel, and the empty pupa case is left protruding from the tunnel at ground level after the moth emerges.  The pupa is brown with one or two transverse rows of dorsal spines on the abdomen. In some species like Synemon plana (Golden Sun-moth) the sexes are strongly dimorphic with the female having bright yellow hindwings, whereas the male has dull brown hindwings. Some isolated small populations of Synemon selene form parthenogenic female groups.   Some studies indicate the early stage brood period requires two years to complete.

There are about 24 recognised species in Australia, and there are possibly more than 20 unamed species.  Many of the latter comprise populations that are very similar and difficult to separate, and will require DNA analysis to establish their true taxonomic relationships.  Seven named species have been recorded from South Australia, and a further three populations are presently unamed or require further study.

 

Synemon discalis Strand, 1911 (Small Orange-spotted Sun-moth). Wing Expanse: 30-36mm. Known Distribution: Southern Eyre Peninsula, Southern Yorke Peninsula, Upper Southeast. Flight Time: Oct-early Nov. Known Hostplants: Gahnia lanigera (Cyperaceae). (Maybe synonymous with S. parthenoides).

Synemon jcaria R. Felder, 1874 (Reddish-orange Sun-moth).  Wing Expanse: 34-40mm. Known Distribution: Upper Southeast. Flight Time: late Jan-mid Mar. Known Hostplants: Lomandra effusa (Dasypogonaceae).

Synemon nais Klug, 1850 (Orange Sun-moth). Wing Expanse: 27-30mm. Known Distribution: East Nullarbor Plains, Far West Coast, Yorke Peninsula, Pinnaroo. Flight Time: late Sep-mid Nov. Known Hostplants: Austrodanthonia setacea and Austrodanthonia sp (Poaceae).

Synemon parthenoides R. Felder, 1874 (Orange-spotted Sun-moth). Wing Expanse: 35-45mm. Known Distribution: Eyre Peninsula, Yorke Peninsula, Mt Lofty Ranges, Kangaroo Island, Upper South East. Flight Time: late October-Jan, rarely to late Feb. Known Hostplants: Lepidosperma carphoides (Cyperaceae), Austrodanthonia sp (Poaceae) .

Synemon plana Walker, 1854 (Golden Sun-moth). Wing Expanse: 31-35mm. Known Distribution: Bordertown. Flight Time: Aug-Mar, mainly Nov-Jan. Known Hostplants: Austrodanthonia carphoides, A. laevis, A. setacea (Poaceae).

Synemon selene Klug, 1850 (Pale Sun-moth). Wing Expanse: 35-52mm. Known Distribution: Two Wells, Lyndoch, Renmark. Flight Time: early Feb-early Mar. Known Hostplants: Austrodanthonia setacea (Poaceae).

Synemon theresa Doubleday, 1846 (Cryptic Sun-moth). Wing Expanse: 28-40mm. Known Distribution: Mt Lofty Ranges, Parkside. Flight Time: Dec-mid Mar.

Synemon sp (Ignita Sun-moth). Wing Expanse: 40-52mm. Known Distribution: Kangaroo Island. Flight Time: Jan. Known Hostplants: Lepidosperma viscidum (Cyperaceae). (Maybe synonymous with S. jcaria).

Synemon sp (Flinders Ranges Sun-moth). Known Distribution: Flinders Ranges. Flight Time: late Oct-early Nov.

Synemon sp (Colona Sun-moth).Wing Expanse: 26mm. Known Distribution: Colona. Flight Time: late Mar.

 

 

 

First instar larva

Photography by R. Grund

 

Author:  R. GRUND, copyright 23 May 2009, all rights reserved.   Last update 23 May 2009.