May 2018 Winning Photograph

One never knows what species will be entered each month – this month’s entries included Andrew Primer’s Eriochilus collinus, John Fennell’s Prasophyllum elatum, Marg Paech’s Pterostylis nutans and the winning picture, Pauline Meyer’s Arachnorchis sp. (which has subsequently been identified as Arachnorchis sp.)

 

1805 sm PM Arachnorchis sp

In the last six years there have been over a dozen photo competition articles (the most recent April 2018) written on some aspects related to Spider Orchids. So, with another Spider Orchid winning the competition it is about time to answer the question – What Is A Spider Orchid?

 

Around the world, the common name Spider Orchid has been bestowed upon a number of orchids in different genera. In Australia, they have principally been applied to a large group within the genus Caladenia, a highly diverse cumbersome genus.

Caladenia in the broad sense is distinguished by erect flower stem and single linear, ovate to lanceolate leaf, (both hairy), labellum distinctly different from the other segments, generally fringed, curved and decorative calli. But within this genus it has been recognised for a long time that there are several distinct but varied groups, which has been reflected in the common names – Dragon, Pink Fingers, Hare, Spider, Wispy Spider, etc.

Consequently in 2001, several segregate genera were published including Arachnorchis for the common named Spider Orchids. This was not widely accepted, as reflected by the Herbaria of Australia. Indeed the original authors are no longer using the segregate names.

Yet despite all that, the segregate names have proved to be very practical for fieldwork. By using the segregate name when species is unknown, extra information is communicated. This was the case with Pauline’s picture. Yes she photographed a Caladenia but which one? It was an Arachnorchis species.

With that in mind, it is time to consider the features that make up a Spider Orchid or Arachnorchis.

In following through a dichotomous key Arachnorchis is immediately separated out from the rest of the Caladenia by the presence of two yellow waxy glands at the base of the column. As this is not the immediate feature seen, the following chart comparing it with the very similar looking Joneseopsis should assist with recognising some of the main distinguishing features.

  SPIDER ORCHIDS
(ARACHNORCHIS)
WISPY SPIDER OR DADDY LONG LEGS
(JONESIOPSIS)
Leaf Sparse to densely hairy
Narrow to broad lanceolate
Red base
Sparsely hairy
Slender
Red base
Stem Wiry densely hairy Hairy wiry
Flower    
Dorsal sepal Erect Erect
Tepals

(Petals & Sepals)

Long & slender with long slender glandular tails or thickened short to long clubs*

Petals and sepals similar size

Narrow, end in very long thin threadlike glandular tails*
Labellum Trilobed
obliquely erect lateral lobes
Midlobe often differently coloured to the base
Small indistinctly lobed

Narrow

  Hinged Hinged
Apex Rolled under at the apex Rolls under*
Margins Fringed with short to long teeth* Short, blunt teeth to smooth
Calli Vary from short rounded crowded to long curved and widely spaced Short blunt congested lamina calli*
  2 or more rows 2 rows*
Basal Gland 2 yellow at  base of the column None
Growth Habit Loose groups* Clumping

 

*Exceptions in all these descriptions

1805 PM Arachnorchis sp Labelled wm

Labelled Features of a Spider Orchid

Reference

Backhouse, G, (2018) Spider Orchids: The Genus Caladenia and Its Relatives in Australia ISBN: 978-0-9946489 Electronic version

Bates, R. J., ed. (2011). South Australian Native Orchids. Electronic version, 2011. NOSSA

Jones, D. L., A Complete Guide to Native Orchids of Australia Including the Island Territories. Reed New Holland

Jones, D. L.; Hopely, T; Duffy, S. M.; Richards, K. J.; Clements, M. A and Zhang X, Australian Orchid Genera an information and identification system. Electronic version, 2006, CSIRO

 

Advertisements

2017 October Winning Picture

1710 JH Arachnorchis tentaculata sm

This month’s theme of “more than six flowers” was interpreted in one of two ways. There were six entries that had six or more plants and the other six entries had six or more flowers, predominately the flowers being on one inflorescence.

The competition was tight with Jane Higgs’ Caladenia tentaculata (syn. Arachnorchis tentaculata) winning by one vote. In South Australia it is known as the King Spider Orchid or Large Green Combed Spider and in Victoria is named the Eastern Mantis Orchid. As it is the largest of the Green Combed Spider Orchids, it is easily identified by its size. But there is variation and sometimes there are patches of small sized plants.

This happened to Rudie Kuiter on one of his orchid forays when he came across of patch of C. parva and small sized C. tentaculata growing together. In his book Orchid Pollinators of Victoria (page 29), he records how he distinguished the differences between the two species – “Except for some minor differences in the labellum they looked much the same. In C. tentaculata the upper margin teeth are longest, whilst in C. parva the central ones are longest. Labellum calli usually run into the red tip on C. parva and just short of the red in C. tentaculata, ...

Though I could not find these details recorded in any of the field guides I consulted, the differences were obvious when comparing the images of C. parva and C. tentaculata on the Retired Aussies website, www.retiredaussies.com

References:

Kuiter, R. H., Orchid Pollinators of Victoria, Fourth Edition. Aquatic Photographics

http://www.retiredaussies.com/ColinsHome%20Page/Orchidssa/Arachnorchis/Arachnorchis%20parva%20SA/Arachnorchis%20parva%20SA11.htm

http://www.retiredaussies.com/ColinsHome%20Page/Orchidssa/Arachnorchis/Arachnorchis%20tentaculata/Arachnorchis%20tentaculata%20King%20Spider%20Orchid.htm

Orchid Basics – Labellums and Columns

Orchids are unique in the floral world. Two distinctive characteristics that set orchids apart from other plants are the labellum and the column.

The labellum is a modified petal.  It is extremely varied in appearance; “often lobed, spurred, adorned with glands, appendages of calli (callus, a hardened swelling or thickening of the skin), sometimes mobile and highly irritable and often brightly coloured”. * The labellum is important for pollination.

The column (as described by Bates and Weber) “is a distinctive feature of all orchids and a unique structure in the plant kingdom. It is formed by fusion of the male parts ‘stamens’ and female organ ‘pistil’.”*

Below are examples of the various types of labellums and columns in some South Australian terrestrial orchids. Each genus has its own characteristic labellum and column.

Sun Orchid

Thelymitra – though the labellum is almost indistinguishable from the other petals and sepals, the column is quite complex.

Hyacinth Orchid

Dipodium or Hyacinth Orchid

Greenhood

Pterostylis or Greenhoods – generally a simple labellum with the column hidden well back into the hood.

Spider Orchid

Arachnorchis (syn Caladenia) can have quite varied and complex, mobile labellums

Helmet Orchid

Corybas or Helmet Orchid – the labellum dominates and the column is hidden deep inside the flower.

Donkey Orchid

Diuris or Donkey Orchid – the labellum is divided giving the appearance of more than one structure.

*Bates and Weber Orchids of South Australia 1990

 

2016 Orchid Picture of the Year

For the final meeting of the year we chose the best of the 2016 monthly winners of the picture competition.

Here in Australia we are fortunate to have such a variety of orchids. They may not be as big and showy as some of the overseas orchids but the diversity of shapes fires the imagination as reflected in this year’s monthly winners, when put together. The common names of the winners – spider, leopard, flying duck, cowslip, zebra, helmet, bluebeard and greenhood – reinforce this theme of diversity.

Patterns and colours contribute to the variety of our orchids. Australian orchid colours run the gamut of the rainbow and more, with Australia being home to most of the naturally occurring blue orchids in the world. This colour fascinates and allures people around the world so much so that nurseries will dye a white orchid blue because it will sell. There is even a website devoted to the colour called, not surprisingly, Blue Orchid  and the popular band master Glenn Miller wrote a song titled Blue Orchids (1944).

Could this be why the very clear winner for the year was Claire Chesson’s Pheladenia deformis common name Bluebeard or Blue Fairy?

  congratulations-clipart-k15686507

  Claire Chesson on your most beautiful picture.

1608-sm-cc-pheladenia-deformis

Pheladenia deformis

Claire won the August competition.

As a reminder, below are the other winners for the year.  Click on the image to see the related articles.

February 2016 Photographer: Pauline Meyers

1602 sm PM Caleana major

Caleana major

March 2016 Photographer: Judy Sara

1603 sm JS Arachnorchis sp

Arachnorchis sp. (Green Combed Spider Orchid

April 2016 Photographer: Claire Chesson

1604 sm CC T benthamaniana

Thelymitra benthamiana

May 2016 Photographer: Pauline Meyers

1605 sm PM Caladenia flava

Caladenia flava

2016 June Photographer: Ros Miller

1606 sm RM Caladenia cairnsiana

Caladenia cairnsiana

2016 July Photographer: Robert Lawrence

1607 sm RWL Corysanthes diemenicus

Corysanthes diemenica (mutation)

2016 September Photographer: Bevin Scholz

1609-sm-bs-pterostylis-cucullata

Pterostylis cucullata

2016 October Photographer: Helen Lawrence

1610-hl-sm-arachnorchis-argocalla

 

Introducing Orchid Pollinators of Victoria: Part One of Two Parts

This week’s blog, Part One of Two Parts, is quoted directly from the introductory chapter (Pages 2&3) Orchid Pollinators of Victoria 4th Edition, 2016, Rudie Kuiter.  Over the years of photographing orchids and their pollinators, Rudie and his team have been discovering much of the hidden world of orchid pollinators.  In this first section he highlights the fallacy of the “one orchid-one pollinator” as well as touching briefly on the vast difference between the insects and their role in the ecosystem.

Click here for Part Two

INTRODUCTION

Amongst flowering plants, orchids have evolved in their own special reproductive ways.  Their pollen is massed as waxy packages, pollinia, unlike like (sic) other flowers that produce masses of fine pollen grains that mostly go astray.  The pollinia are relatively heavy and the usually small creatures need to be strong fliers for cross pollination (see image below).  Orchids evolved with amazing strategies to attract specific carriers in order to transfer pollen between flowers of their species only, and in this way eliminating the need to produce great quantities.  Various insects, many moths, bees and even birds have been documented as pollinators of orchids around the world (v.d. Cingel, 2001).  A number of uniquely different examples of orchids attracting insects for their pollination evolved in Australia, especially in the more temperate southern zones originating from Gondwana times.  With very few exceptions the Victorian orchids are terrestrial, ground-dwellers, that rely on small insects such as fungus-gnats, native bees, wasps, ants and many attract only the males by sexual deception.  In the case no pollinators visits, many species may self-pollinate as a back up.

When taking an interest in orchids it seems difficult enough to identify some species.  Usually one looks and admires the amazing flowers that may resemble an insect and can be difficult to recognise as a flower at first.  An insect on a flower may be thought of something that spoils a picture – until taking an interest in the visitor!

160219 Anita Marquart Melangyna collatus on Caladenia rigida

Hoverfly on Caladenia rigida (syn Arachnorchis rigida)

I first learned about the orchid pollinators in Orchids of South Australia by Bates & Weber, 1990, an excellent book by today’s standard, but few were seen over the years by just being there at the right time when photographing orchids.  During preparation of the book on Caladenia spider-orchids, certain issues developed from questionable statements made in scientific papers about wasp-pollinators.  Of particular concern was about the one-to-one relationship – how only one wasp-species would be involved with only one spider-orchid species – and suggesting populations that were thought to represent the same species comprised different taxa if not pollinated by the same wasp-species.  A very different story emerged when monitoring the local spider-orchid populations to find the answers and it became clear that there was much more to it.  A site in Wonthaggi with a very large colony of Caladenia dilatata proved to be perfect for this study and also to photograph pollinators as it produces flowers for about four months.  It was found that a local wasp-pollinator species typically flies for a little over one month, thus this need to be investigated further.  Scientific publications on wasp-pollinators were generally based on short-term experiments, and usually employing baiting methods – moving flowers and often taking them to different sites.  Responses included unnatural behaviour or attracting sibling wasps at a non-local site.  It is certainly true that a particular flower may attract only one species of wasp a t a locality and a certain time in the season, but this reflects a very small part of the picture.  It can be different in the long-term, at certain localities or with a season.

The main study site was in coastal dunes, where in a very large population of Caladenia dilatata produced flowers for over four months from September, and under favourable Summer-conditions into January.  At least three congeneric (belonging to the same genus) thynniid wasps species were involved in this population.  The flying times were up to about 6 weeks for each wasp species, that were separated or slightly overlapping.  The flowering times in other populations of C. dilatata in Wonthaggi and Wilsons Promontory were usually about one month in each, and at the corresponding times to the study site the wasps visiting were the same species.  A close sibling C. parva in the Wonthaggi heathland habitats and early flowering C. dilatata were pollinated by the same species, but the later flowering C. tentaculata by a thynniid wasp of the different genus.

160219 Anita Marquart Melangyna collatus with pollinia

Hoverfly with pollinia

Whilst a flower may attract only one wasp species, the kairomones (chemical omitted by the orchid to attract a pollinator)  of a species may vary between flowers within in a population or when allopatric (growing in different geographical regions), just like colour or morphology.  Variations maybe in relation to locality, weather conditions, or ground chemistry and available pollinator.  Pollinators may evolve over time, but adaptions usually require many seasons and this would vary with location.  The observations made over several seasons suggest that more than one congeneric insect is involved in pollination depending on local or seasonal conditions, especially after a long drought.  Chiloglottis gunnii populations in Langwarrin were checked for pollinators since a decade-long drought and no action was seen for many seasons.  When wasps finally made an appearance they comprised different taxa of Neozeleboria the first season, but only one became the common and principal pollinator the following seasons.  Thynniid wasps are very localised as females lack wings and rely on the males to carry them around during copulation and to provide food.  It limits their travelling and their homing range may comprise just a few hundred metres.  Thynniid wasp are very vulnerable in small reserves isolated by land-clearing, and certain species have gone locally extinct due to conducting burns.  Insects form a crucial and fundamental part of an ecosystem, but their importance is never considered in the planned burning, showing a complete lack of understanding by people in charge.  So little is known of ecosystem’s foundations, but controlled burning continues – ruining precious habitats.  Orchid species failing to produce seed pods is an indication that pollinators were absent, probably gone locally extinct.  Orchid species that have a sexual association with thynniid wasp pollinators are localised and usually have geographically variable flowers.  The situation is different with Cryptostylis spp. And their pollinating male wasp Lissopimpla excelsa, as females are a strong flyers.  The flowers of Cryptostylis are geographically uniform in each species and the wasp is widespread.  Both sexes are very distinctive in colour that show no variation.  They are active over Spring and Summer and are great travellers.

To be continued …

Orchid Hunter Visits Kuipto

The following video is by Orchid Hunter, Julian Pitcher.  Julian is concerned about the conservation of orchids and is also keen to teach others about Australia’s unique orchids.  At the time of the visit, Julian was resident in Victoria; now he resides in Queensland.  Enjoy an interstate visitor’s view of our beautiful orchids.

WHAT ORCHID IS THIS? HOW PHOTOS CAN HELP! – Part One of Two Parts

The following article is from the April 2016 Journal of the Native Orchid Society of South Australia.  The article is complete in itself but Part Two of this post will illustrate how images can help with images of Crytostylis robusta and C. reniformis.

Orchids are beautiful plants and many of us like to capture that beauty on photographs. And there are many beautiful pictures around.

Many times NOSSA, the Herbarium and other specialist groups receive images requesting identification but the vital information is missing.

When photographing for identification, it is necessary to take more than one image, particularly if you are unable to easily return to the site for more images. When in doubt, take several shots from many different angles highlighting different features of the plant and its habitat.

Another very important point to remember is, when there are several of the same plant, to photograph the orchid that is most representative of the group, not the atypical or unusual plant.

General Guide

As a general guide, it is helpful to take a picture of each of the following

  • whole plant
  • individual flower – both from the front and the side, occasionally the back.
  • flower head
  • leaf or leaves
  • habitat

Other helpful things to consider photographing are:

  • capsules of the finished flower – sometimes it can yield useful information.
  • for some genera, the stem can also be a helpful feature as between some species there can be a difference in the hairiness of the stem.
  • It is also worth including in a photograph an indication of whether the plants are growing in colonies with others or as scattered individual plants.

Importance of Size

It is also good to give an idea of size, this can be as simple as using a thumb or hand, a coin (show the reverse not the head) or any item that had an easily recognized size. It is important to have the object next to the feature being photographed. For example, a coin on the ground next to a leaf or a hand immediately behind the flower gives a clear indication of size. Remember to take another photo without the hand or coin.

Some Specific Identifying Features

Some species are distinctive and easily recognised, eg the Flying Duck Orchid, but others are not and it is helpful to know what part of the plant to photograph as different genera will have different identifying features.

  • Spider orchids – the tips of the segments (petals and sepals) and details of the labellum are important
  • Sun orchids – the column in the middle, the ovary at the base of the flower, and the number of bracts (leaf-like growth) on the stems
  • Pink fingers – the length of the leaf in comparison with the length of the flower stalk; also the back of the flower is helpful
  • Gnat orchid – the leaf is the best identifying feature, but also the bud can be helpful
  • Hyacinth orchid (of the Adelaide Hills) – labellum
  • Mosquito, Mayfly and Helmet orchids when not in flower – both sides of the leaf
  • Gastrodia – the flower spike
  • Rufoushoods – side view of the flower and close up of the labellum as the hairs on or surrounding the labellum are important features.
  • Leek Orchids – the labellum is very important, as well as part if not all of the flower spike as the distance between the individual flowers aids identification
  • Greenhoods – if present, the non-flowering rosette of leaves

The Australian Virtual Herbarium has some good tips for photographing flower. Click here to visit the site

 

Spider Orchid

Spider Orchid Photo: Robert Lawrence

This image lacks the ends of the segments to determine the identification.  The presence or absence of  clubs on the ends of the segments (petals and sepals) can often be the distinguishing feature with many of the Arachnorchis (Spider Orchids).

Atypical Cyrtostylis leaves

These leaves are an unusual shape and by themselves are not suitable for identification

November 2015 Winning Photograph

November’s theme was hybrids. Orchids, more than any other plant family, are likely to produce natural hybrids. Even though the overall occurrence of natural hybridisation in orchids is low, it occurs often enough to make some species identification challenging.

Hybrids mainly occur between species of the same genera such as Jenny Pauley’s Arachnorchis brumalis x A. conferta

11sm JP Arachnorchis brumalis x conferta

Arachnorchis brumalis x A. conferta

but, less commonly, it can occur between genera as seen with Pauline Meyer’s Caladenia latifolia x A. brumalis

11 sm PM C latifolia X A brumalis

Caladenia latifolia x Arachnorchis brumalis

and her Western Australian photograph of Caladenia x enigma; a hybrid between C. falcata and Drakonorchis barbarossa.

11sm PM Caladenia x enigma

Caladenia x enigma


Jones (2006) states that “Natural hybrids are more common in some genera, such as Arachnorchis, Caladenia and Diuris, than in others.” To this list could be added Thelymitra as seen with both of the winning pictures T. x truncata and T. x irregularis. Interestingly with these two hybrids, the parents are not always the same; the parents for T. irregularis could be T. ixiodies or T. juncifolia with either T. carnea or T. rubra.

11 sm RAL Thelymitra x irregularis.jpg

Thelymitra
x irregularis

A similar situation occurs with T. truncata with the parents consisting of T. juncifolia and any member of the T. pauciflora (including T. albiflora, T. arenaria, T. bracteata, T. brevifolia, T. cyanapicata, T. pauciflora) or of the T. nuda complex.

11 sm RWL Thelymitra x truncata

Thelymitra
x truncata

The conditions necessary for hybridisation are that the parents must grow in the same area, have overlapping flowering time and share the pollinator. Brown et al (2103) make the additional observation – Hybrids are more common between wasp and bee-pollinated species than between two wasp-pollinated species or two bee-pollinated species.   … However, rare hybrids between species using the same pollination strategies, do occasionally occur …

Obviously hybridisation is more likely to occur when there is an abundance of the parent species. This situation can occur when there is mass flowering following fires or good seasonal rains. Site disturbances either through natural causes or clearing can result in increased incidence of hybridisation.

Hybrids are often infertile and will only last for the life of the individual plant but some have the ability to reproduce vegetatively and, provided the conditions remain favourable, may persist for several years.

One situation that can occur is hybrid swarm. When these occur they can make orchid identification challenging. Hybrids share the characteristic of both parents and by careful observation this can be deduced but swarms introduce an added complexity because the hybrid can backcross with either of the parents or cross fertilise with themselves. The result is a wide range of variation which makes orchid identification difficult.

Finally, some orchids will not hybridise even though the conditions are right. This could be due to specific pollinator or possibly chemical or genetic barriers.

References:

Brown et al (2013) Field Guide to the Orchids of Western Australia, Floreat, WA, Simon Nevill Publications

Jeans, Jeffrey & Backhouse, Gary (2006) Wild Orchids of Victoria, Seaford Vic, Aquatic Photographics

Jones, David (1988) Native Orchids of Australia, Frenchs Forest, NSW, Reed Books

Jones, David (2006) A Complete Guide to Native Orchids of Australia including the Islands and Territories, Frenchs Forest, NSW, Reed New Holland

Introduction to Australian Orchidaceae CD-ROM

https://www.anbg.gov.au/cpbr/cd-keys/orchidkey/html/intro-c_hybrid.html   accessed 7th December 2015

Bates, Robert (2011) South Australia’s Native Orchids NOSSA DVD Adelaide

Spotted Pink Sun Orchid – Beautiful, but Only a Hybrid

https://nossa.org.au/2014/09/26/thelymitra-x-irregularis-beautiful-but-only-a-hybrid/ accessed 7th December 2015

 

 

2015 August Winning Photograph

08 RP Arachnorchis cardiochila smOf the five entries this month, three were spider orchids and the winner was from this group. It was Rob Pauley’s Arachnorchis cardiochila (syn Caladenia cardiochila), Heart Lip Spider Orchid which can be found across South Australia and into western Victoria. At one time a specimen was found on Flinders Island, Tasmania but as it was collected in 1947 it is considered extinct in that region.

This lovely flower is quite variable in colour and form.

The heart shape labellum is a distinctive feature of this spider orchid, so it is not surprising that this is reflected in the name. Cardio means heart and chila lip.

What probably is surprising is that the traditional heart shape symbol has come full circle. It had a botanical origin. According to cardiologist Professor Armin Dietz the symbol was originally a stylized vine/ivy leaf as evidenced from paintings on goblets from the 3rd millennium. In the Middle Ages, doctors and anatomists used the shape to represent the heart. As at that time Latin and Greek were both the international languages of scholars, including doctors, the word associated with the symbol was the Greek word kardia (ie cardio) meaning heart. Consequently, by the time Ralph Tate names this species in 1887, the shape has become intrinsically linked with the heart and so it must have appeared to him as an obvious descriptive name.

There are several field guides which give a detailed description of the species including South Australia’s Native Orchids DVD-ROM which is available for sale from NOSSA.

 

References:

http://www.heartsymbol.com/english/index.html accessed 28th August 2015

The texts published on this website are taken from his book “Ewige Herzen – Kleine Kulturgeschichte der Herzbestattungen” (“Eternal Hearts – a short cultural history of heart burials”), published 1998 in MMV Medien und Medizin Verlag, Munich. (English translation by Pauline Liesenfeld.)

http://data.rbg.vic.gov.au/vicflora/flora/taxon/bca2495d-3325-4c1b-b2c3-782566fb6bce accessed 28th August 2015

http://dpipwe.tas.gov.au/Documents/Caladenia-cardiochila-listing-statement.pdf acessed 28th August 2015

 

2014 November Photograph Competition Part 1

11 sm CD Arachnorchis sp with hover fly

With a theme of Orchids and Insects for the November meeting it was hoped that there would be some entries with pollinators and therefore there would be two categories Insect Visitors and Pollinators. This month’s article will feature the Pollinator section and Insect Visitors in the next month.

In all there were four potential pollinator photographs. The insects were either scrounging around at the base of the column or else they had the pollinia attached to them. Unfortunately only one was a true pollinator so the category became Insects with Pollinia. The winning photograph of Arachnorchis brumalis with an unidentified hoverfly was taken by Chris Davey. Interestingly the other two pictures also featured Arachnorchis species with the hover fly Simosyrphus grandicornis. Resembling a wasp but minus the sting, this species is one of the common hover flies native to Australia.

Called Hover Flies owing to their ability to hover motionless in one spot, they are also known as Flower Flies because they are often found hovering around as well as pollinating flowers. It is not surprising, therefore, to find them around orchids. Yet instead of being called pollinators they are non-pollinators (Bates & Weber 1990). They visit the orchids, forage inside the flower and may even manage to collect some pollinia but that is all. They may not necessarily visit another flower of the same species but if they do, they will fail to deliver the pollinia to the stigma2.

Rudie Kuiter agrees with Bates that hover flies are not orchid pollinators but just when we think we have worked it out he adds “but we have at least one orchid in Victoria that is pollinated by hoverflies and witnessed now several times and this is Caladenia catenata” (synonym Petalochilus catenatus). Notwithstanding the case for this species, it would appear that in most cases hoverflies remove pollinia so that it is not available to a more specific pollinator.

Why then are the hover flies attracted to the orchids? Is it for food? An internet image search revealed that hover flies visit the flowers of many different genera including Thelymitra and Diuris. This is interesting because flowers are the food source for hover flies but though many orchids promise food, many species do not produce the nectar and pollen (as a food source) that they desire. Diuris and Thelymitra belong to this group of non-nectar producing flower. Other orchids that don’t produce nectar include Gastrodia, Dipodium and the Duck orchids. Again, there are orchids such as Crytostylis which produce minimal nectar and with Prasophyllum the nectar is hidden in cells that require puncturing – not a good food source!

Having discussed hover flies as non-pollinators, in this month’s competition, which photograph had a pollinator? – It came last and was Robert Lawrence’s photograph of a native bee on a Dipodium pardalinum, another non-nectar producing orchid. The story of this photograph was featured in Photographing Orchid Pollinators, April 2014 Journal as well as in a previous blog on Photographing Pollinators.

References:

Smith James, Information Centre, South Australian Museum, personal communications

Kuiter Rudie personal communications

Bates and Weber, Orchids of South Australia, 1990

Australian Museum, http://australianmuseum.net.au/Hover-flies Accessed 4th December 2014

Brown, et al, Field Guide to the Orchids of Western Australia, 2013

Jones, Native Orchids of Australia Including the Island Territories, 2006

Bates, South Australia’s Native Orchids 2011 DVD-ROM

Martin, The Vocabulary of Orchids: An Amateur’s Perspective, 2005

1Pollinia is basically a coherent compact mass of pollen that allows the pollen to be transported as a single unit

2The stigma is a sticky depression (or swelling) at the front of the column, the receiving surface for the pollinia that is necessary for germination.