Overview
The Dundas Spider Orchid (Caladenia dundasiae) is an exquisite and threatened terrestrial orchid endemic to the red loam soils and York gum woodlands of the Western Australian Wheatbelt. Named in honor of botanical artist and conservationist Judy Dundas, this striking spider orchid is admired for its warm reddish-brown and pinkish-cream coloration, drooping filiform sepal tips, and intricately fringed labellum.
Biology and Physical Characteristics
Caladenia dundasiae produces a solitary, erect, densely hairy basal leaf up to 18 centimeters long. In early spring (August to September), a hairy reddish-green stem rises up to 40 centimeters, bearing one or two large, elegant flowers spanning up to 10 centimeters across. The sepals and petals are spreading and arching, colored deep terracotta-red or creamy pink with dark reddish mid-veins, tapering into narrow, glandular osmophore-bearing tips. The broad labellum is pale cream with red transverse stripes, fringed along its margin with slender, curved teeth and studded with four dense rows of red-headed calli.
Behavior and Ecology
Flowering during the peak of the austral spring, Caladenia dundasiae uses sexual deception to accomplish pollination. The glandular osmophore tips of the sepals disperse airborne volatile compounds that mimic the sex pheromones of female thynnid wasps. Male wasps follow the scent trail to the orchid, attempting to clasp the mobile, callus-covered labellum and inadvertently striking the reproductive column to achieve cross-pollination.
Conservation and Human Impact
Caladenia dundasiae is officially listed as Vulnerable due to historical large-scale land clearing for grain cropping across the Wheatbelt, which has left populations restricted to isolated woodland remnants and roadside reserves. Current conservation priorities focus on fencing remnant populations to exclude rabbits and sheep, controlling invasive agricultural weeds, and managing roadside maintenance activities to avoid disrupting delicate topsoil seed banks.
Interesting Factoid
This orchid was named in tribute to Judy Dundas, who spent decades documenting and illustrating the rare and threatened flora of the Western Australian Wheatbelt.
Last updated: October 2026