Cyrtostylis robusta, commonly known as large gnat-orchid or mosquito orchid, is a species of orchid endemic to southern Australia. It usually has a single more or less round leaf and a flowering spike with up to seven reddish flowers with a shelf-like labellum.
Cyrtostylis robusta is a terrestrial, perennial, deciduous, herb with a single heart-shaped, kidney-shaped or almost round leaf NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. The leaf is light to medium green on the upper surface and silvery on the lower side. Between two and seven pinkish red flowers NaNsigfig=1NaNsigfig=1 long and about 6sigfig=1NaNsigfig=1 wide are borne on a flowering stem NaNsigfig=1NaNsigfig=1 high. The pedicel is NaNsigfig=1NaNsigfig=1 long with a bract at its base. The dorsal sepal is erect and curved forward, linear but tapered, NaNsigfig=1NaNsigfig=1 long and about 2.5sigfig=1NaNsigfig=1 wide. The lateral sepals are linear, NaNsigfig=2NaNsigfig=2 long, 1sigfig=1NaNsigfig=1 wide and curve forwards or downwards. The petals are similar in size and shape to the lateral sepals and curve forwards or slightly downwards. The labellum is oblong, NaNsigfig=1NaNsigfig=1 long and NaNsigfig=2NaNsigfig=2 wide and slopes slightly downwards with a few serrations near its pointed tip. Flowering occurs from May to October.[1] [2] [3]
This species is similar to C. huegelii in Western Australia but usually has fewer, more brightly-coloured flowers with a wider labellum.[4] In South Australia is can be distinguished from the similar C. reniformis which has more heavily veined leaves and are green on the lower side.[5]
Cyrtostylis robusta was first formally described in 1987 by David Jones and Mark Clements. The description was published in the journal Lindleyana from a specimen collected near Jerramungup.[6] The specific epithet (robusta) is a Latin word meaning "oaken" or "strong like oak".[7]
The large gnat orchid occurs in southern Victoria where it grows in coastal scrub and forest. It is found in south-eastern South Australia including Kangaroo Island and in Tasmania. It is most common and widespread in the south-west of Western Australia where it grows in near-coastal shrubland, woodland and forest between Perth and Israelite Bay.
Cyrtostylis robusta is listed as "rare" in Tasmania under the Threatened Species Protection Act 1995.[8]