Indicative distribution
The areas shown in pink and/purple are the sub-regions where the species or community is known or predicted to occur. They may not occur thoughout the sub-region but may be restricted to certain areas.
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click here to see geographic restrictions).
The information presented in this map is only indicative and may contain errors and omissions.
Scientific name: Ocybadistes knightorum
Gazetted date:
20 Dec 2002
Profile last updated:
01 Dec 2017
Description
The Black Grass-dart Butterfly is a small skipper with a wingspan of only 18-19mm. The uppersides of the wings are dark brown-black with orange markings, while the undersides are generally lighter. The Black Grass-dart Butterfly is distinguished from similar species by its small size, darker appearance (due to the less extensive orange markings on the upperside) and the pattern of discrete orange patches on the upper forewing. The caterpillars are pale jade green and up to 25mm long.
Distribution
The Black Grass-dart Butterfly occurs only on the NSW mid north coast from Coffs Harbour to Scotts Head. It is currently known from two disjunct areas: a northern population centred around Sawtell and a southern population along Warrell Creek. The butterfly is restricted to areas supporting its larval food plant Floyd's Grass Alexfloydia repens, which is also listed as an Endangered species in NSW. Habitat is located on floodplain alluvial deposits between 1m and 2m above the mean tide level, although there are two atypical headland occurences (at Coffs Harbour and Sawtell).
Habitat and ecology
- The Black Grass-dart Butterfly is considered to be monophageous, with Floyd's Grass Alexfloydia repens being the only larval food plant known. The butterfly is generally restricted to within about 50m of suitable patches of Floyd's Grass.
- Habitat is predominantly located in swamp sclerophyll forest where Swamp Oak Casuarina glauca and/or Broad-leaved Paperbark Melaleuca quinquenervia are usually the dominant canopy species. The larval food plant Floyd's Grass favours the moderate to high sunlight levels in this habitat.
- High salinity levels are not tolerated by Floyd's Grass. The majority of its distribution is between 1m and 2m above the mean tide level, i.e. immediatley above the zone of king tide inundation.
- The most vigorous and extensive examples of Floyd's Grass are found on rich alluvial floodplain terraces. However, the grass will grow on a wide variety of substrates, e.g. it is found on two coastal headlands.
- The Black Grass-dart Butterfly is generally found in riparian zones within 5km of the coast. However, it reaches inland along Warrell Ck as far as Macksville (over 7km from the coast).
- The Black Grass-dart Butterfly appears to be a multi-voltine species with several overlapping generations each year. The eggs are laid on the underside near the tip of the leaf of Floyd's Grass, with the first instar emerging after 12-14 days. The pupal stage normally lasts 14-16 days, however the winter brood is slow to develop and eggs laid in April/ May do not produce adults until September/October.
- In captivity, adult butterflies live for 10–16 days, with 16 days estimated to be
near their maximum adult lifespan in the wild. The flight period extends from very late August to early May, although the butterflies are most abundant from September to March.
Regional distribution and habitat
Click on a region below to view detailed distribution, habitat and vegetation information.
Threats
- Invasion by weeds, particularly Lantana (Lantana camara), broad-leaved Paspalum (Paspalum mandiocanum), blue billygoat weed (Ageratum houstonianum) and trad (Tradescantia fluminensis) that out-compete key larval food species (Floyd's grass).
- Sea-level rise due to climate change has the potential to inundate populations or create unsuitably saline conditions.
- Fire is the greatest threat for populations occurring on peat soils that can sustain a fire for an extended period.
- Stochastic risk of extinction due to the highly restricted distribution of key populations and potential for degrading genetic effects (e.g. inbreeding depression).
- Grazing by domestic stock.
- Loss of habitat due to the direct and indirect impacts from nearby urban activities (e.g. camping, fires, other disturbance).
Recovery strategies
Priority actions are the specific, practical things that must be done to recover a threatened species, population or ecological
community. The Office of Environment and Heritage has identified
7 priority actions
to help recover the Black Grass-dart Butterfly in New South Wales.
Activities to assist this species
- Prevent regular burning of habitat areas.
- Avoid slashing potential habitat areas.
- Protect streams from pollution.
- Protect habitat from grazing and disturbance by fencing.
- Assist with weed control programs in habitat areas.
- Identify potential sea-level rise refugia for habitat.
- Report records of this species to the DECCW.
Information sources
- Andren, M. and Cameron, M.A. (2012) The distribution of the endangered Black Grass-dart Butterfly Ocybadistes knightorum (Lepidoptera: Hesperiidae). Australian Zoologist 36: 159–168
- Braby, M.F. (2016) The complete guide to butterflies of Australia. (CSIRO Publishing, Melbourne)
- Lambkin, T.A. and Donaldson, J.F. (1994) A new species of Ocybadistes Heron (Lepidoptera: Hesperiidae) from Australia. Australian Entomologist 21: 15-20.
- Sands, D.P.A. and New, T.R. (2002) The Action Plan for Australian Butterflies.
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