August 2014 Winning Photograph

08 sm CC Caladenia valida

Claire Chesson’s Arachnorchis valida (common name Robust Spider Orchid) was the winning photograph for August.

The name Arachnorchis valida was not validated until 2002; synonym Caladenia valida. Previously it had been included under Caladenia huegelii (a Western Australian species) and Caladenia reticulata.

A. valida grows in sandy or sand over red clay soil, in sheltered clearings within heathy woodland or mallee but within a very restricted and disjunct distribution on Fleurieu Peninsula and Kangaroo Island in South Australia; and Otway Plain, Victoria. Rated Endangered in South Australia, it is not listed nationally.

Although A. valida shares some similar features with A. reticulata (ie 1 to 2 flowers, clubbed sepals, calli on the labellum) it also has quite distinctive features (see chart below) that help to differentiate between the two as they can sometimes be found growing together.

Comparison of A. valida and A. reticulata

Features

A. valida

A. reticulata

Pollinating wasp Phymatothynnus pygidialis Phymatothynnus victor
Leaf Felted Leaf – dense, short hairsSemi erect Very long silky hairs; purplish at the baseErect
Flower Stem Taller – 40 cm, hairy 30 cm, green & purplish red with long silky hairs
Flower Size Though variable, larger – 7 cm 5 cm
Flower Greenish when first opened fading to white or cream as the flower matures Red-brown
Perianth Stiffly spreading – broad based sepals; backswept petalsNo stripes Dorsal sepal erect; perianth spreading downwardRed stripes
Labellum Can be red but without veining Red with veining

 

NB: November Picture Competition Theme – Orchids and Insects

See the 2014 April Journal for hints of photographing orchid pollinators.

References:

http://www.rbg.vic.gov.au/dbpages/dev/vicflora/index.php/viclist/name/4677 accessed 4th September 2014

Threatened Species Profile Fact Sheet Caladenia valida Department for Environment and Heritage, South Australia

International Plant Name Index – http://www.ipni.org/

Personal communications with Claire Chesson

South Australia’s Native Orchids DVD 2011 Bates

Spider-orchids the Genus Caladenia and it Relatives in Australia CD 2011 Gary Backhouse

 

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