SOUTH AUSTRALIAN SUN MOTHS


The sun-moths belong in the Castniid Family, which presently contains the single genus Synemon. 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, and in warm conditions 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.

The larvae feed on grasses, low tussock sedges and mat-rushes.  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 are of wichetty 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 tunnel, and the empty pupa case is left protruding from the tunnel at ground level after the moth emerges.  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. 

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 four populations are presently unamed or require further study.

 

Synemon discalis Strand, 1911 Gahnia lanigera (Cyperaceae) Sth EP-SYP-USE. Small Orange-spotted SM.

Synemon jcaria R. Felder, 1874  Lomandra effusa (Dasypogonaceae) Up SE. Reddish-orange SM.

Synemon nais Klug, 1850 Austrodanthonia setacea and sp (Poaceae) east Nullarbor, Colona-YP-Pinnaroo. Orange SM

Synemon parthenoides R. Felder, 1874 Lepidosperma carphoides (Cyperaceae), Austrodanthonia sp (Poaceae) EP-YP-MtLoftyRang-KI-USE. Orange-spotted SM

Synemon plana Walker, 1854 Austrodanthonia carphoides, A. laevis, A. setacea (Poaceae) Up SE, Golden SM

Synemon selene Klug, 1850 Austrodanthonia setacea (Poaceae) (Fabian Douglas pers. comm.) Lyndoch, Two Wells, Renmark, Adel Plains, Pale Sunmoth

Synemon theresa Doubleday, 1846  SthMtLofty, Parkside, 7Hill. Cryptic SM

Synemon sp ignita Lepidosperma viscidum (Cyperaceae) KI

Synemon sp Flinders Ranges

Synemon sp Far West Coast

Synemon 'discalis' Port Lincoln

 

 

 

First instar larva

Photography by R. Grund

 

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