Caladenia longicauda subsp. rigidula
Caladenia longicauda" subsp. "rigidula, commonly known as the rigid white spider orchid or island white spider orchid, is a plant in the orchid family Orchidaceae and is endemic to the south-west of Western Australia. It has a single hairy leaf and up to three large, mainly white flowers with relatively short lateral sepals and petals. It is similar to the reclining white spider orchid ("C. cruscula") but that species has smaller, cream-coloured flowers. Description. "Caladenia longicauda" subsp. "rigidula" is a terrestrial, perennial, deciduous, herb with an underground tuber and which usually grows as solitary  plants. It has a single hairy leaf, long and wide. Up to three, mainly white flowers long and wide are borne on a spike tall. The dorsal sepal is erect, long and wide. The lateral sepals are long and wide, the petals are long and wide and all spread horizontally near their bases then turn slightly downwards. The labellum is white, long, wide with narrow teeth, up to long along its edges. There are usually two or four rows of pale red calli up to long in the centre of the labellum. Flowering occurs from August to early October. This  subspecies is similar to "Caladenia cruscula" but has larger white flowers rather than creamy-yellow ones. Taxonomy and naming. "Caladenia longicauda" was first formally described by John Lindley in 1840 and the description was published in "A Sketch of the Vegetation of the Swan River Colony". In 2001 Stephen Hopper and Andrew Brown described eleven subspecies, including subspecies "rigidula" and the descriptions were published in "Nuytsia". The subspecies name ("rigidula") is the diminutive form of the Latin word meaning "stiff", "hard" or "inflexible" hence "rather rigid", referring to the stiffly spreading sepals and petals of this subspecies. Distribution and habitat . The rigid white spider orchid mainly occurs between Ravensthorpe and Israelite Bay in the Coolgardie, Esperance Plains and Mallee biogeographic regions where it grows in moist places including in shallow soil on granite outcrops. Conservation. "Caladenia longicauda" subsp. "rigidula" is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.