Cryptostylis, commonly known as tongue orchids, is a genus of approximately 25 terrestrial orchid species belonging to the family Orchidaceae (order Asparagales). The genus was first formally described in 1810 by the Scottish botanist Robert Brown in his landmark work Prodromus Florae Novae Hollandiae et Insulae Van Diemen, in which he described three founding species: C. ovata, C. erecta, and C. longifolia (the last now treated as C. subulata).
Tongue orchids are perennial herbs growing from a thick, branching underground rhizome; unlike many orchids they lack tubers entirely, instead producing thick, fleshy roots. Most species bear one to a few stalked, erect leaves, often tinged purple on the lower surface, though one species — Cryptostylis hunteriana — is entirely leafless and saprophytic. The inflorescence is a raceme of one to several dull-coloured, non-resupinate flowers. The defining floral feature is the prominent labellum, which attaches at the base of the column and closely envelops it — an arrangement reflected in the genus name, derived from the Ancient Greek kryptos ("hidden") and stylos ("column").
Molecular phylogenetic work has placed Cryptostylis within the tribe Diurideae, revising its earlier assignment to Cranichideae. Together with the New Caledonian endemic genus Coilochilus, it constitutes the subtribe Cryptostylidinae. The genus ranges from India, Sri Lanka, Thailand, Taiwan, the Philippines, and Malaysia through Indonesia to Australia, New Zealand, New Caledonia, Vanuatu, and Samoa. Five species occur in Australia, three of them endemic.
Cryptostylis is particularly celebrated in pollination biology. All Australian species are pollinated solely by the male ichneumon wasp Lissopimpla excelsa (the orchid dupe wasp), which attempts to copulate with the flower in a behaviour termed pseudocopulation — first documented by Australian naturalist Edith Coleman in 1928. Uniquely, Lissopimpla excelsa males have been observed ejecting seminal fluid during these encounters, a phenomenon not recorded in any other orchid genus. The wasp appears more strongly attracted to the orchid flowers than to actual female wasps, and gas chromatography has identified a single active chemical compound responsible for this attraction across multiple Cryptostylis species.
Etymology
The genus name Cryptostylis derives from the Ancient Greek kryptos ("hidden") and stylos ("pillar" or "column"), referring to the floral column of these orchids, which is partly concealed by the large, enveloping labellum. The name was coined by Robert Brown when he formally described the genus in 1810.
Distribution
Cryptostylis comprises around 25 species distributed across a broad Indo-Pacific arc: from India and Sri Lanka through Thailand, Taiwan, the Philippines, and Malaysia to Indonesia, then south and east to Australia, New Zealand, New Caledonia, Vanuatu, and Samoa. Five species occur in Australia, of which three are endemic. Within this range, tongue orchids inhabit temperate to tropical environments and tolerate both well-drained and swampy substrates.
Ecology
All Australian Cryptostylis species are pollinated exclusively by male ichneumon wasps (Lissopimpla excelsa, the orchid dupe wasp), which are deceived into attempting copulation with the flower — a mechanism called pseudocopulation, first described by Edith Coleman in 1928. The flowers closely resemble female wasp body parts under hymenopteran vision (green, blue, and ultraviolet wavelengths), even though they appear dissimilar to human eyes. Notably, Cryptostylis is the only orchid genus in which the male pollinator has been observed ejecting sperm-containing seminal fluid during pseudocopulation. Despite multiple species sharing the same pollinator and occasionally growing together, natural hybridisation does not occur.
Taxonomy
Cryptostylis was established by Robert Brown in 1810 (Prodromus Florae Novae Hollandiae et Insulae Van Diemen), with three original species and no nominated type. Molecular phylogenetics places the genus in tribe Diurideae of Orchidaceae, correcting the earlier placement in Cranichideae. Cryptostylis and the New Caledonian endemic Coilochilus together form the subtribe Cryptostylidinae. GBIF recognises the genus within Orchidaceae, order Asparagales.
