This endangered butterfly is found along a small stretch of the NSW Mid North Coast and is a subtropical endemic of the NSW North Coast.
Conservation Status in NSW: Endangered
Commonwealth Status: Not Listed
The Black Grass-dart Butterfly has a highly restricted distribution along the Mid North Coast. It is unique due to its sole reliance on Floyds grass (Alexfloydia), which it uses for both feeding and as a host plant for its larvae. Both the Black Grass-dart Butterfly and its host plant are listed as endangered in NSW.
The north-east region of NSW is known for its high butterfly species richness. By learning more about the habitat requirements of this species and the actions that support population growth, we can help protect the natural environment we value and ensure these species can continue to survive.
Identification:
The Black Grass-dart Butterfly is a small butterfly that shares features with similar species. However, its smaller size and darker colouring help distinguish it from others.
- Wingspan: 18–19 mm
- Upper side of wings: Dark brown to black with orange markings
- Under side of wings: Similar pattern to the upper side, but lighter in colour
- Caterpillar: Approximately 25 mm long and pale jade green
(Department of the Environment and Energy, 2017)
Habitat & Diet:
The Black Grass- dart Butterfly relies entirely on Floyd’s Grass (Alexfloydia repens) as its larval food plant and is usually found within 50 metres of where the grass grows. Its preferred habitat is coastal swamp sclerophyll forest, typically dominated by Swamp Oak or Broad-leaved Paperbark.
Floyd’s Grass favours moderate to high sunlight, low salinity, and areas just above king tide inundation, most commonly on fertile floodplain terraces. As a result, the Black Grass-dart Butterfly is mainly found in riparian areas within 5 km of the coast, though it can occur further inland.
The species breeds several times a year, with adults most active from September to March. Adults live only a few weeks, while the winter generation develops slowly, emerging in spring.
(NSW Department of Climate Change, Energy, the Environment and Water, 2024)
Distribution:
The Black Grass-dart Butterfly is endemic to the NSW Mid North Coast and has a highly restricted distribution. Confirmed records occur at scattered locations between Coffs Harbour and Sawtell, where suitable habitat remains. Similar habitat conditions are also present in the Port Macquarie region, particularly in coastal and riparian areas that support Floyd’s grass. While formal surveys in this area have been limited, the presence of suitable habitat suggests the species is likely to occur locally.
Image: Known area of the Black Grass-dart Butterfly (Office of Environment and Heritage, 2017)
What can you do?
At a state level, the Office of Environment and Heritage have identified seven priority actions to help the recovery of the Black Grass-dart Butterfly in NSW which can be found here. As a community we can help by addressing the following.
Avoid regular burning in known and potential habitat areas.
Limit slashing in areas where suitable habitat may be present.
Protect streams and waterways from pollution.
Use fencing where needed to reduce grazing and other disturbance.
Support weed control programs in and around habitat areas.
Identify and protect areas that could act as refuges from sea-level rise.
Report any sightings of the Black Grass-dart Butterfly to the NSW Department of Climate Change, Energy, the Environment and Water (DCCEEW).
Under Threat:
Key threats to this species include:
Invasion by weeds such as lantana, broad-leaved paspalum, blue billygoat weed and trad, which out-compete Floyd’s grass, the butterfly’s larval food plant.
Sea-level rise linked to climate change, which may flood habitat or increase soil salinity beyond tolerable levels.
Fire, particularly in peat soils, which can burn for long periods and cause severe habitat damage.
A high risk of local extinction due to the species’ very limited distribution and reduced genetic diversity.
Grazing by domestic stock.
Habitat loss and disturbance from nearby urban activities, including camping, fire and repeated human use.
(NSW Department of Climate Change, Energy, the Environment and Water, 2024)
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Reference List:
Andren, M., & Cameron, M. A. (2014). The conservation status of the Black Grass-dart Butterfly, Ocybadistes knightorum: A species at risk from climate change. Australian Zoologist, 37(1), 76–84. https://doi.org/10.7882/AZ.2014.008
iNaturalist. (n.d.). Observations of Ocybadistes knightorum [Webpage]. iNaturalist. Retrieved [date you accessed], from https://www.inaturalist.org/observations?taxon_id=1147770
NSW Government, Department of Planning and Environment. (2017, December 1). Black Grass-dart Butterfly profile [Threatened species profile]. NSW BioNet – Threatened Biodiversity. https://threatenedspecies.bionet.nsw.gov.au/profile?id=10573
NSW Government, Department of Planning and Environment. (2018, August 20). Floyd’s Grass (Alexfloydia repens) profile [Threatened species profile]. NSW BioNet – Threatened Biodiversity. https://threatenedspecies.bionet.nsw.gov.au/profile?id=10036
NSW Government, Department of Planning and Environment. (2017, December 1). Black Grass-dart Butterfly (Ocybadistes knightorum) profile [Threatened species profile]. NSW BioNet – Threatened Biodiversity. https://threatenedspecies.bionet.nsw.gov.au/profile?id=10573
