The nomenclature and taxonomic status of Ogyris waterhouseri is revised and considered to be specifically distinct from Ogyris idmo (Hewitson 1862) based on fundamental differences in juvenile and adult morphology. For the past 94 years, O. waterhouseri has been treated either as a geographical subspecies or as synonym of O. idmo, and for the last 36 years it has been known under the name O. idmo halmaturia (Tepper 1890), which we show to be a junior synonym of O. otanes (C. & R. Felder 1865). Assessment of the conservation status of O. waterhouseri indicates that the butterfly warrants listing as Endangered nationally according to IUCN criteria. The species is restricted to habitats comprising heathland, mallee-heathland or mallee low open-woodland with a heath understorey on sand where colonies of the associated ant, Camponotus terebrans Lowne, 1865, occur abundantly. Ogyris waterhouseri formerly had a wide range in the coastal and semi-arid areas of southern Australia (western and south-western Victoria, southern South Australia); however, its geographic range is estimated to have contracted by about 88-98%, primarily due to habitat loss. Currently, the species is known from only two fragmented populations comprising a total of six extant sites. The common name Eastern Bronze Azure is proposed for O. waterhouseri.

The diversity and abundance of native invertebrates is declining globally, which could have significant consequences for ecosystem functioning. Declines are likely to be at least as severe as those observed for vertebrates, although often are difficult to quantify due to a lack of historic baseline data and limited monitoring effort. The Lepidoptera are well studied in Australia compared with other invertebrates, so we know that some species are imperilled or declining. Despite this, few butterfly taxa are explicitly listed for protection by legislation. Here we aim to identify the butterfly taxa that would most benefit from listing by determining the Australian butterflies at most immediate risk of extinction. We also identify the research and management actions needed to retain them. For 26 taxa identified by experts and various conservation schedules, we used structured expert elicitation to estimate the probability of extinction within 20 years (i.e. by 2040) and to identify key threatening processes, priority research and management needs. Collation and analysis of expert opinion indicated that one taxon, the laced fritillary (Argynnis hyperbius inconstans), is particularly imperilled, and that four taxa (Jalmenus eubulus, Jalmenus aridus, Hypochrysops piceatus and Oreisplanus munionga larana) have a moderate–high (>30%) risk of extinction by 2040. Mapped distributions of the 26 butterflies revealed that most are endemic to a single state or territory, and that many occupy narrow ranges. Inappropriate fire regimes, habitat loss and fragmentation (through agricultural practices), invasive species (mostly through habitat degradation caused by weeds and rabbits) and climate change were the most prevalent threats affecting the taxa considered. Increased resourcing and management intervention will be required to prevent these extinctions. We provide specific recommendations for averting such losses.

The Golden‐rayed Blue, Candalides noelkeri sp. nov. (Lepidoptera: Lycaenidae), from the Wimmera of western Victoria, Australia, is described and illustrated. The male and female genitalia and immature stages are figured, described and compared with those of Candalides heathi and C. xanthospilos. Candalides noelkeri sp. nov. is placed in the C. xanthospilos species‐group, being most closely allied to and allopatric with C. heathi. It is predominantly univoltine, with adults usually present from late November to early February. However, it has a facultative pupal diapause that gives rise to a partial overlapping second generation in mid‐summer. The species is ecologically specialized, monophagous and has a narrow geographical range, currently known only from two localities in a restricted area near Natimuk. Within this limited area it is restricted to flood plains bordering natural salt‐lakes where the larval food plant, a prostrate form of Myoporum parvifolium (Myoporaceae), grows as a low spreading ground cover plant. Morphological and geological evidence suggest a recent (late Pleistocene) allopatric speciation event between C. noelkeri sp. nov. and C. heathi. The small, peripheral spatial distribution of C. noelkeri sp. nov. implies that differentiation has been achieved by the founder effect, either through peripheral isolates speciation (peripatric speciation) or postspeciation dispersal, possibly as a result of a barrier created by the volcanic plains in western Victoria. Available information indicates that C. noelkeri sp. nov., Victoria's only endemic species of butterfly, is facing a high risk of extinction and accordingly its conservation status should be considered as Endangered. The most serious threat at the type locality is habitat change or succession caused by invasion of Melaleuca halmaturorum, which is creating a dense shaded paperbark forest that is reducing both the preferred open sunny microhabitat and the extent of the larval food plant. Recognition of C. noelkeri sp. nov. as a flagship taxon is likely to enhance the conservation of biodiversity in remnant flood plain/salt‐lake ecosystems of temperate south‐eastern Australia. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 81, 275–299.

Although changes, particularly declines, in Australian terrestrial insects and other invertebrates have long been suspected and well‐documented for some species, the magnitude, rate and spatial extent of decline remain unclear. Here we use a combination of alternative, qualitative approaches (expert opinion, historical records and temporal replication of surveys) to standardised monitoring and mapping programs to investigate the extent of change of a peri‐urban butterfly assemblage. This assemblage, comprising 52 species, of which 46 are residents or seasonal immigrants, was studied at three spatial scales (local ~0.01 km2, intermediate ~9 km2 and regional ~100 km2) in the Eltham district near Melbourne based on presence/absence data over the past 40 (1981–2020) and 80 years (1941–2020). We then consider the causal factors or drivers that have led to changes, and we explore the timing and ecological patterns underpinning extirpations. Long‐term records reveal substantial changes (mostly decline) in composition and species richness of the 46 breeding species at all spatial scales and time frames analysed. Although the magnitude and rate of decline were higher at the smaller, local to intermediate scales (29–43% decline over 40 years, loss rate of 0.20–0.25 species/year) compared with the larger, regional scale (26% decline over 80 years, loss rate of 0.15 species/year), extirpations at the larger scale were more alarming because they are indicative of widespread population collapse. Declines in relative abundance and occupancy were also recorded at the intermediate and regional spatial scales. Further decline (extinction debt) is anticipated for several ecological specialists currently known from very few sites. Historical extirpations mostly involved obligate myrmecophilous lycaenids and appear to have been largely driven by a combination of urbanisation (habitat loss, degradation and fragmentation) and vegetation encroachment. More recent extirpations consist mainly of grass‐feeding and mistletoe‐feeding specialists and are more worrying because they have predominantly occurred within the past 20–30 years. An interaction of urbanisation (tree canopy death and decline of mistletoes and their host trees from ecosystem dysfunction) and climate change (water stress and heat waves) are considered to be the most likely drivers for these ecological guilds.

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