Deciduous terrestrials. Pseudobulbs short, fleshy, ovoid, subterranean, replaced annually. Each pseudobulb and its leaves last a single season. Leaves narrow, thin-textured, plicate, petiolate. Racemes long, arising from the apex of a current years new growth. Peduncle 4-sided, with a low wing-like structure on each angle. Flowers lasting several days, relatively thin-textured, dull-coloured. Perianth segments narrow, with recurved margins, usually reflexing or recurving away from the labellum. Lateral sepals shorter and broader than the dorsal sepal, closely subtending the labellum. Labellum much broader than the other segments, reflexed sharply near the middle. Callus consisting of two small rounded basal calli with an extended central plate. Column relatively long, narrow, incurved, prominently winged.
Significant Generic Characters
Deciduous terrestrial orchids; pseudobulbs replaced annually, subterranean, short, fleshy, ovoid; leaves lasting one season, narrow, thin-textured plicate; racemes terminal on a current seasons growth, erect; peduncle 4-sided, with a low wing-like structure on each angle; flowers lasting several days, relatively thin-textured, dull-coloured; perianth segments often with recurved margins, reflexed or recurved; dorsal sepal narrower than the lateral sepals; petals narrower than the sepals; lateral sepals closely subtending the labellum; labellum stiffly attached to the column base, much broader than the other segments, reflexed sharply near the middle; callus consisting of two small basal calli with an extended central plate; column narrow, incurved, prominently winged.
Size and Distribution
A genus of c.6 species distributed in parts of tropical Asia with a single species, Empusa habenarina, extending to northern Australia. It is distributed in northern parts of the Northern Territory, including Melville Island (11°20' S) and in Queensland occurs on the islands of Saibai (9°25' S) and Moa (10°15' S) in Torres Strait and on the mainland from Cape York (10°41' S) south to the border and in northern New South Wales south to near Coffs Harbour (30°18' S). State occurrence: Northern Territory, Queensland, New South Wales.
Ecology
In Australia Empusa habenarina is distributed from the coastal lowlands to about 600m alt. and ranges from the tropics to warm temperate regions. It grows in open forest, wallum and heath in soils ranging from freely draining to those that are seasonally inundated. In the tropics the prevailing climate has a summer wet season between December and March with the remaining months being much drier with sporadic or intermittent rain. In warm temperate regions the growth and flowering of this species is heavily dependant on summer and autumn rains.
Biology
Pollination: The flowers of Empusa habenarina last several days and are insect-pollinated but the vector remains unknown.
Reproduction: Reproduction in Empusa habenarina is solely from seed. Seed dispersal takes 2-3 months from pollination and the capsules develop in an erect position. Apomixis is unknown in the genus.
Seasonal Growth: The plants grow actively during the summer months and become completely leafless and dormant over winter and spring.
Flowering : Flowering occurs during summer and autumn.
Hybrids: Natural hybrids involving species of Empusa are unknown.
Derivation
Empusa is derived from the Greek, Empusa, a hobgoblin with a vampire's appetite and a custom of travelling in the form of various animals. The original author apparently saw some fanciful resemblance to a hobgoblin in the flowers of these orchids.
Botanical Description
Perennial, deciduous, terrestrial herbs, sympodial. Plants glabrous. Roots filamentous, produced from the base of a newly maturing pseudobulb. Stems absent. Pseudobulbs present, subterranean, short, ovoid to conical, fleshy, multiple-noded, each lasting a single season. Trichomes absent. Leaves lasting a single season, lateral and apical, few per shoot, sheathing at the base, without a distinct petiole, the lamina narrow, thin, conduplicate. Venation acrodromus to campylodromus, with numerous cross-veinlets. Inflorescence racemose, terminal, few to several-flowered, erect, arising with the new growth. Peduncle longer than the rhachis, usually 4-angled, winged along the angles, with very few small, projecting sterile bracts. Floral bracts small, free. Ovary elongate, curved, sometimes twisted, with irregular ribs. Flowers resupinate, widely spaced to moderately crowded, dull coloured (green, yellowish, orange or reddish), pedicellate. Dorsal sepal free, longer and narrower than the lateral sepals, often recurved or reflexed; margins revolute. Lateral sepals free, asymmetric, much shorter and broader than the dorsal sepal, projecting forwards as a pair and closely subtending the labellum. Petals of similar length to the dorsal sepal but much narrower; margins revolute. Labellum fixed by its base to the anterior column base, immoveable, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina entire, usually sharply reflexed back on itself near the middle; margins entire; apex entire, apiculate or emarginate. Spur absent. Callus consisting of two, small, rounded basal calli and an extended low, flat, central plate. Nectar usually present. Column lacking free filament and style, elongated, incurved distally. Column wings present, mainly apical, well-developed. Column foot absent. Pseudospur absent. Anther terminal, 2-celled, persistent, basifixed, porrect, smooth, rostrate. Pollinarium absent. Pollinia 4 in 2 pairs, hemispherical, yellow or orange, hard, waxy. Viscidium absent. Rostellum ventral, transverse, protruding. Stigma entire, transverse, concave. Capsules dehiscent, glabrous, erect; peduncle not elongated in fruit; pedicels elongated in fruit. Seeds numerous, light coloured, winged.
Taxonomy
Species of Empusa have traditionally been included in Liparis but recent molecular studies have shown that the recognition of several genera in the Liparis complex is justified.
Nomenclature
Empusa Lindl. in Edwards', Bot. Reg. 10: sub.t. 825 (1 Sept. 1824); Liparis subgenus Sturmia Schltr. Type species: Empusa paradoxa Lindl.
References
Dockrill, A.W. (1969). Australian Indigenous Orchids. Volume 1. The Society for Growing Australian Plants, Halstead Press, Sydney.
Dockrill, A.W. (1992). Australian Indigenous Orchids. Volume 1 & 2. Surrey Beatty & Sons in association with The Society for Growing Australian Plants, Chipping Norton, NSW.
Jones, D.L. & Clements, M.A. (2004). Miscellaneous new species, new genera, reinstated genera and new combinations in Australian Orchidaceae. Orchadian 14(8), Scientific Supplement XIV.
Schlechter, R. (1982 English translation). The Orchidaceae of German New Guinea, Australian Orchid Foundation.