''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 The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each se ...

of Western Australia. It has a single hairy leaf and up to three large, mainly white flowers with relatively short lateral sepals and

petal Petals are modified Leaf, leaves that surround the reproductive parts of flowers. They are often advertising coloration, brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''c ...

s. It is similar to the reclining white spider orchid ('' C. cruscula'') but that species has smaller, cream-coloured flowers. Caladenia longicauda rigidula 02

Description

''Caladenia longicauda'' subsp. ''rigidula'' is a terrestrial, perennial, deciduous,

herb In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal ...

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 John Lindley FRS (5 February 1799 – 1 November 1865) was an English botanist, gardener and orchidologist. Early years Born in Catton, near Norwich, England, John Lindley was one of four children of George and Mary Lindley. George Lindley w ...

in 1840 and the description was published in ''

A Sketch of the Vegetation of the Swan River Colony "A Sketch of the Vegetation of the Swan River Colony", also known by its standard botanical abbreviation ''Sketch Veg. Swan R.'', is an 1839 article by John Lindley on the flora of the Swan River Colony. Nearly 300 new species were published in it, ...

''. In 2001

Stephen Hopper Stephen Donald Hopper AC FLS FTSE (born 18 June 1951) is a Western Australian botanist. He graduated in Biology, specialising in conservation biology and vascular plants. Hopper has written eight books, and has over 200 publications to his n ...

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 Ravensthorpe may refer to any of the following places. England *Ravensthorpe, Dewsbury in West Yorkshire **Ravensthorpe railway station, Dewsbury *Ravensthorpe, Northamptonshire *Ravensthorpe, Peterborough in Cambridgeshire *Ravensthorpe, an histor ...

and

Israelite Bay Israelite Bay is a bay and locality on the south coast of Western Australia. Situated in the Shire of Esperance local government area, it lies east of Esperance and the Cape Arid National Park, within the Nuytsland Nature Reserve and the Grea ...

in the Coolgardie, Esperance Plains and Mallee

biogeographic regions A biogeographic realm or ecozone is the broadest biogeographic division of Earth's land surface, based on distributional patterns of terrestrial organisms. They are subdivided into bioregions, which are further subdivided into ecoregions. De ...

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 The Department of Parks and Wildlife (DPaW) was the department of the Government of Western Australia responsible for managing lands described in the ''Conservation and Land Management Act 1984'' and implementing the state's conservation and e ...

References

{{Taxonbar, from=Q26205515 longicauda subsp. rigidula Endemic orchids of Australia Orchids of Western Australia Plants described in 2001 Taxa named by Stephen Hopper Taxa named by Andrew Phillip Brown