Black grass-dart butterfly (Ocybadistes knightorum) - endangered species listing
The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Black Grass-dart Butterfly Ocybadistes knightorum Lambkin & Donaldson, 1994 as an ENDANGERED SPECIES in Part 1 of Schedule 1 of the Act. Listing of endangered species is provided for by Part 2 of the Act.
NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. Ocybadistes knightorum is described by Braby (2000) as: Wingspan: male 19 mm; female 18 mm. Upperside: dark brown-black: fore wing with cell and basal half of costa orange, an irregular postmedian band of three orange spots, a subapical band of three orange spots, two orange subterminal spots between veins M1 and M3 and a faint orange streak along dorsum; hind wing with an obscure orange subbasal spot in cell, and a broad orange postmedian band from vein M1 to 1A+2A. Underside: ground colour dark brown-black suffused with yellow, spots and bands similar to upperside but yellow. The male can be distinguished from the female by the presence of a broad patch of black sex-scales which extends from just above vein M3 to 1A+2A on the upperside of the fore wing. In the female the tergum of the wings is more rounded, the markings on the upperside are yellower, and the suffusion of yellow scales on the underside is less extensive. Immature stages. Egg: 0.8 mm wide, 0.5 mm high; white to pale cream when laid; dome shaped and smooth. Larva: up to 25 mm long; body pale green except prothoracic and anal segments pale blue-green, with faint darker green middorsal line; head pale yellow-brown with dark and pale brown variable longitudinal bands. Pupa: 13-15 mm long; pale brown to greenish-brown becoming darker at anterior and posterior ends.
2. Ocybadistes knightorum is monophagous on the grass Alexfloydia repens (Sands 1997). Adults have been recorded from September to December and again in February and April suggesting that two or more generations occur annually. Eggs are laid on the underside near the tip of a leaf of the larval food plant. Larvae construct a longitudinal tubular shelter at the base of the leaf and rest inside the shelter for much of the day and night emerging to feed at dusk and dawn. Pupation takes place inside a shelter of dead leaves and litter joined by silk. Adults fly close to the larval food plant and are active in sunny or warm conditions. Flight activity is limited to between mid-morning and mid-afternoon. Males establish territories.
3. The butterfly has been recorded in northern New South Wales coastal lowland open-forest with a dense overstorey of Casuarina glauca with some Melaleuca quinquenervia and an open, grassy understorey. The food plant is limited to semi-saline habitats in the king-tide zone above mangrove communities. Two colonies occur in reserves.
4. Ocybadistes knightorum is only known from several discrete colonies south of Coffs Harbour, New South Wales and is limited to patches of Alexfloydia repens. The host plant only occurs in small discrete patches and thus, all known colonies of O. knightorum are similarly restricted.
5. Alexfloydia repens is threatened by coastal development and at all sites by weeds, especially Broad-leaf Paspalum ( Paspalum wittsteinii), Lantana ( Lantana camara) , Bridal creeper ( Asparagus asparagoides) and Groundsel Bush ( Baccharis halimfolia). Alexfloydia repens is listed as an endangered species in Part 1 of Schedule 1 of the Act. These threats to Alexfloydia repens will limit development of the larval food plant and reduce open space in the overstorey in which adults fly.
In view of the above the Scientific Committee is of the opinion that Black Grass-dart Butterfly Ocybadistes knightorum Lambkin & Donaldson, 1994 is likely to become extinct in nature in New South Wales unless the circumstances and factors threatening its survival or evolutionary development cease to operate.
Proposed Gazettal date: 20/12/02
Exhibition period: 20/12/02 - 07/02/03
The NSW Threatened Species Scientific Committee undertook a review of this species in 2022 and found that the threat status is unchanged. The Conservation assessment report may be downloaded: Conservation assessment report Ocybadistes knightorum (PDF 360KB).
References
Braby, M.F. (2000).Butterflies of Australia: their identification, biology and distribution. (CSIRO Publishing, Melbourne).
Sands, D. P. A. (1997). Alexfloydia repens Simon: a food plant for Ocybadistes knightorum Lambkin & Donaldson (Lepidoptera: Hesperiidae) and their conservation significance. Australian Entomologist 24, 117-118.