GOLDEN SUN MOTH SYNEMON PLANA ACTION PLAN 186 Golden Sun Moth Action Plan PREAMBLE The Golden Sun Moth (Synemon plana Walker, 1854) was declared an endangered species on 15 April 1996 (Instrument No. DI1996-29 under the Nature Conservation Act 1980). Under section 101 of the Nature Conservation Act 2014, the Conservator of Flora and Fauna is responsible for preparing a draft action plan for listed species. The first action plan for this species was prepared in 1998 (ACT Government 1998). This revised edition supersedes the earlier edition. This action plan includes the ACT Native Grassland Conservation Strategy set out in schedule 1 to the ‘Nature Conservation (Native Grassland) Action Plans 2017’, to the extent it is relevant. Measures proposed in this action plan complement those proposed in the action plans for Natural Temperate Grassland, Yellow Box/Red Gum Grassy Woodland, and component threatened species such as the Striped Legless Lizard (Delma impar) and the Grassland Earless Dragon (Tympanocryptis pinguicolla). need to maintain natural evolutionary CONSERVATION STATUS processes. Synemon plana is recognised as a threatened Specific objectives of the action plan are to: species in the following sources: • Conserve large populations in the ACT. National Protect other populations from unintended impacts (unintended impacts are those not Critically Endangered – Environment Protection already considered through an and Biodiversity Conservation Act 1999 environmental assessment or other statutory (Commonwealth). process). Australian Capital Territory • Manage the species and its habitat to maintain the potential for evolutionary Endangered – Nature Conservation Act 2014. development in the wild. Special Protection Status Species - Nature Conservation Act 2014. • Enhance the long-term viability of populations through management of New South Wales adjacent grassland to increase habitat area Endangered – Threatened Species Conservation and connect populations. Act 1995. Victoria SPECIES DESCRIPTION AND Threatened – Flora and Fauna Guarantee Act ECOLOGY 1988. DESCRIPTION The Golden Sun Moth (Synemon plana Walker 1854) is a moth in the family Castniidae. Genera CONSERVATION OBJECTIVES in this family are found in Central and South The overall conservation objective of this action America and in Australia, suggesting a plan is to maintain in the long term viable, wild Gondwanan origin for the family (Edwards populations of S. plana as a component of the 1991). All adult moths in this family are diurnal, indigenous biological resources of the ACT and and their larvae feed on monocotyledonous as a contribution to regional and national plants (Common 1990). conservation of the species. This includes the Golden Sun Moth Action Plan 187 Synemon plana adults are medium-sized, with two centuries later this had been reduced to clubbed antennae and no functional mouth- less than 1% of the original area (Kirkpatrick parts. In males, the upper side of the forewing is 1993), with the remaining remnants degraded dark brown with pale grey patterning, the hind by stock grazing and weed invasion. wing is dark bronzy brown with dark brown A recent review of the status of S. plana across patches, and the underside of both wings is its range found that between the years 2000 mostly pale grey with dark brown spots. and 2010 the known area of occupied habitat In females the upper side of the forewing is dark had increased from 10 km² to 150 km² due grey with pale grey patterning, the hind wing is mainly to increased survey of areas proposed bright orange with black submarginal spots, and for development (Hogg 2010). Currently, the the underside of both wings is silky white with species is known from 100 (mainly small) sites small black submarginal spots. The male north and west of Melbourne and in south-west wingspan is about 34 mm, and the female Victoria (Brown and Tolsma 2010; Brown et al. wingspan is about 31 mm. The male having a 2011; DSE 2013), 48 sites in NSW (OEH 2012) larger wingspan than the female is unique in the and 78 sites in the ACT. Australian Castniidae. Females have a long Most of the populations of S. plana in the ACT extensible ovipositor. region are smaller than five hectares and lie Synemon plana eggs are just over 2 mm long, within an area about 100 km long and 30 km and the larvae develop underground where they wide, extending from the Queanbeyan district in are found associated with the roots of a few the south-east to the Boorowa area in the species of grasses or at the upper end of silk- north-west (Clarke and Whyte 2003; NSW lined tunnels below the tussock base (Richter Wildlife Atlas 2015). In the ACT the species 2010). Larvae are cream in colour, and late- occurs in lowland areas adjacent to the city of instars have a red-brown head capsule. The Canberra, and in mostly small sites within the empty red-brown pupal cases protrude from the city (Table 1). ground, usually at the base of or close to a grass Table 1 shows the area of habitat at sites where tussock. The pupal cases of female moths are the species is known to occur in the ACT. These larger than those of males, reflecting the larger sites are defined as areas of contiguous, size of the gravid female abdomen (Richter apparently suitable habitat, rather than by land 2010). ownership/management. For example, relatively large areas of habitat at Canberra Airport and the Majura Training Area are DISTRIBUTION AND ABUNDANCE counted as one site because the habitat is Historically S. plana was widespread in south- continuous across the tenure boundary, while eastern Australia and relatively continuous two small areas of habitat at the University of throughout its range, showing a close Canberra are counted as two sites because they correlation with the distribution of temperate are separated by more than 200 metres of non- grasslands dominated by Wallaby Grasses habitat. (Rytidosperma spp., formerly Austrodanthonia) Because males are unlikely to fly more than 100 (Edwards 1993; O’Dwyer and Attiwill 1999). m away from suitable habitat (Clarke and Areas dominated by Wallaby Grasses probably O’Dwyer 2000), and females move even less occurred as part of a grassland mosaic, distance, populations separated by 200 metres interspersed with patches dominated by other or more are likely to be isolated and are grass species. Museum records indicate S. plana therefore treated as separate sites. was still common and widespread prior to 1950, Populations of S. plana tend to have a patchy with collections showing its distribution distribution (and density) within an area of extended from Bathurst, NSW, through the apparently suitable habitat (and this area can Southern Tablelands of NSW and central vary between years), which means actual areas Victoria to the South Australian border (Edwards occupied by S. plana are likely to be less than 1993). the habitat areas shown in Table 1. The area of temperate grassland in Australia at the time of European settlement is estimated to have been about two million hectares, though 188 Golden Sun Moth Action Plan Table 1. Location of Synemon plana populations earlier on north facing sites, those with light in the ACT ground cover and drier sites (Edwards 1994). More adults emerge on hot dry days, making it District Number of Habitat area difficult to detect the difference between long- sites (hectares) term population trends and short-term seasonal Belconnen 9 355 effects at a site without surveying the whole site on every day of a season. Mark–release– Central 25 110 recapture studies are labour-intensive and need Canberra to be carried out every day of the flying season in order to estimate the number of adult males Gungahlin 32 812 present in the population. The length of the larval period is not clear, nor is Jerrabomberra 7 60 it known if it can vary according to environmental conditions, so it is not known Majura 5 466 what proportion of the standing population is represented by the number of adults that fly in Total 78 1803 one season. Detecting and sampling larvae is difficult due to their patchy subterranean distribution and is destructive of larvae and The area of apparently suitable (or potential) their habitat. Late-season surveys of above- habitat for S. plana in the ACT is estimated to be ground pupal cases can provide a useful about 1800 hectares, with individual sites indication of S. plana density as well as locations varying in size from 0.055 ha to more than 300 where larvae have developed underground ha, and a median size of 2.8 ha. There are large because pupal cases are readily recognisable populations on Commonwealth Land at the and have been found to persist in the field for Majura Training Area and Canberra Airport in longer than three weeks. However, pupal cases the Majura Valley, at the Lawson Grasslands are likely to be more difficult to find on sites (former Belconnen Naval Transmission Station with denser vegetation or in wetter years site) and at the West Macgregor offset area. (Richter et al. 2012; Rowell pers. obs). Less extensive populations occur in the Dunlop Grasslands Reserve and Jarramlee Nature Population estimates based on mark–release– Reserve in Belconnen, in the Jerrabomberra recapture surveys have been undertaken four Grasslands (east and west), and in the times for the small (0.4 ha) site at York Park in Mulanggari, Crace, Mulligans Flat and Barton. The number of flying males was Goorooyarroo nature reserves in Gungahlin. estimated to be 520 (1992), 456 (1993) and 736 et al. Based on the known former distribution of (1994) (Harwood 1995), giving an average lowland Temperate Grassland in the ACT and population estimate for those years of 1400 areas surveyed for S. plana, it is unlikely any males per hectare This would be an annual adult significant populations of the species remain cohort of about 2300 per hectare if the undiscovered.