Clarification of Pterostylis valida

Short Paper 3 Identity of Pterostylis valida (Orchidaceae) by Rudie Kuiter was published in June 2017. In this paper, Rudie has tackled the difficult group of Rustyhoods or Oliogochaetochilus (specifically Pterostylis valida) within the genus Pterostylis. Many of the different species occur in isolated pockets over a wide geographical range. Differences can be subtle but Rudie has sought to clarify the distinction between P. valida  and similar species. Click here read the complete paper.

A typical flower at the type-locality, green with the usual stripes on the transparent parts of the hood, cup-shaped synsepalum and dark labellum swellings. Opposite page Image of the original 1941 description page by Nicholls of Pterostylis valida as a variety of P. squamata. It was cropped with the deletion of the description of Caladenia hastata, the other species. 

A typical flower at the type-locality, green with the usual stripes on the transparent parts of the hood, cup-shaped synsepalum and dark labellum swellings. (Image from Rudie Kuiter’s Short Paper)

 

Advertisements

Pterostylis Pollinators

Rudie Kuiter et al have been observing orchid pollinators over many seasons spending hours watching and becoming familiar with pollinator interaction with the orchid, learning when to anticipate pollination activity.

Their observations of various Pterostylis species has been documented in Overview of Pterostylis Pollination (Orchidaceae) in Victoria. In all, they observed 53 Pterostylis species and 40 species of pollinators from several different genera. They noted that some pollinators species were active most of the day but others were only active in the late afternoon whilst others were “only seen on dusk and possibly are nocturnal as well”.

 

 

It Finally Happened …

“The person who first records the whole pollination event will be very lucky indeed.” So wrote Bob Bates (South Australia’s Native Orchids, 2011). He was referring to the pollination event for Bearded Greenhoods in the genus Plumatichilos. As with many orchids there has always been a lot of conjecture about the pollination strategy involved so it is good to finally have photographic evidence of a previously unknown pollinator.

For several years now Rudie Kuiter, Mitchell Findlater-Smith and Rober Lindhe have been researching the relationship between orchids and insects, spending much time in the field observing and photographing the insects. Finally they have managed to obtain a photograph of a pollinator but it was not one of their photographs. Instead it was Neil Blair who took the photograph and observed a dagger fly pollinating a Plumatichilos. The male of these fascinating insects catches another insect and offers it for a nuptial gift to a female in order to be accepted as a mate. The photographs are amazing. It’s worth reading the paper Pollination of the Bearded Greenhoods (Orchidaceae) by Dagger Flies (Diptera: Empididae) just to see the pictures.

plumatochilos-sp-woodland-sm

Introducing Orchid Pollinators of Victoria: Part Two of Two Parts

Continuing last week’s blog, here is the completion of Rudie Kuiter’s Introducion, Orchid Pollinators of Victoria. In this section he discusses some factors of hybridisation and the value of regular observation by local people interested in orchids.

Click here for Part One

Lissopimpla excelsa is the pollinator of all members of Cryptostylis, but hybrids are not known, even when sympatric, thus a molecular mechanism is in place that prevents cross-fertilisation.  Hybrids in other orchid genera do occur and these usually are amongst closely related species. Several congeneric orchids attract the same male pollinator species, thus would be emitting the same kairomones, the scent that is a mimic of the female’s sex-pheromones, but normally these orchids are allopatric or have different habitat preferences.  The land clearing, frequent fires, changes of watercourses, gold-diggings are amongst many unnatural human habitat interference of recent times.  Historically in undisturbed natural habitats sibling orchid species that attracted the same male insect were not sympatric, not flowering at the same time or were in close vicinity to each other.  In disturbed sites the situation has changed, as closely related species may have become sympatric and hybridisation take place.  Spider-orchids that attract thyniid wasps with kairomones normally target a certain local species, but many allopatric species are know to share the same pollinator and readily hybridise where they became sympatric.  In Pterostylis greenhoods the known hybrids are also caused when different species attract the same pollinators.

Cryptostylis subulata 008

Cryptostylis subulata (Moose Orchid)

We still have much to learn to fully understand how adaptable the orchids are, the role insects play and how to interpret what we see.  Orchids are finely tuned to their world and can change and adapt in ways that most people seem to underestimate.  I requires observations of the same plants over many seasons to get a good understanding of their variability and  adaptability.  Unusual forms often show after a drought or fire may look like a new species, but soon change back to typical or normal within a few good seasons or after regeneration.  It is usually the local people taking an interest that see the changes in the same plants over time that dispute what the ‘on-the-fly’ taxonomist come up with.

Creatures evolved as part of an endless combination of life-forms, ranging from microscopic to the tallest tree, that together form an ecosystem in which all organisms depend on each other.  The climate, weather and other factors changes the environment constantly that influence the members differently, dome doing better than others, but it collectively maintains a balance.  Natural events such as a major fire or flood may benefit environments in areas as part of seemingly long cycles, but they are very short in evolutionary terms.  Unnatural man-made fires are very destructive as these are conducted much too frequently, wrong time of the year, and in the wrong place.  Not obvious, but also very detrimental is the use of insecticides that seems to effect the Diptera members the most.  Many of the important pollinators such as the fungus-gnats have gone locally extinct and most of the Pterostylis depend on them.  To work with the pollinators it is essential to have a good understand of the life-cycles of the insects involved and watch the flowers in the wild.  After witnessing Pollinator behaviours of the fungus-gnat on Pterostylis nutans countless times, the principal pollinator is easily recognised with other species.  Unfortunately few good areas to find orchids and learn about their pollinators are left.  Many are now rare and measures taken to protect them usually focuses on just a species.  To be effective their habitat area and surrounding needs to be cared for, letting the natives grow and have the natural canopy reform.  At least, habitats should be protected from further disturbances, especially by badly informed governmental environment departments with their fires.

Pollinator and Corunastylis archeri

Pollinator with pollinia

Note This book is solely based on first-hand observations on the orchid-pollinators in the wild.  Descriptions and comments are from many hours of watching each species over multiple seasons.

Apart from Orchid Pollinators of Victoria, Rudie Kuiter has produced several Victorian orchid books.  If you are interested in purchasing any please contact us.

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 …

Orchids, Insects and Fire

Recently, 10th February 2016, Anita Marquart, PhD student, Adelaide University spoke at the Field Naturalists Society of South Australia. She is a recipient of the Society’s Lirabenda Endowment Fund Research Grant.   At the meeting she gave a summary of her research – Orchids, Insects and Fire: Investigating the impacts of prescribe burning on orchid pollinators in Southern Australia. Though she has not finished collating the data she has kindly supplied a summary of her talk with her preliminary findings.

It is always encouraging to see research on our native orchids. They are the Barometer of the Bush, so the more we can discover about them, hopefully the more we will better understand how to manage our native bushland.

 

Orchids, Insects and Fire: Investigating the impacts of prescribed burning on orchid pollinators in Southern Australia

Anita Marquart, Renate Faast, José M. Facelli, Andrew Austin

School of Earth and Environmental Sciences,

The University of Adelaide, Adelaide 5005 Australia

PhD Project

Summary

Fire is an important ecological factor in Australian ecosystems. Orchids that depend on specific pollinators may be more susceptible to disturbance than more generalist species. Therefore, declines or changes in pollinator communities due to prescribed burns and wild fires could lead to reduced pollination success and consequently declines in orchid populations. The project combines traditional plant and insect ecology with advanced molecular techniques to identify orchid pollinators and assess their response to prescribed burns and wild fires. Insect relevant habitat characteristics (such as floral abundance, vegetation height, presence of logs, litter and standing litter) were assessed and trapping surveys of potential orchid pollinators were conducted in spring, before and after prescribed burns. The effect of both spring burns and autumn burns is being investigated.

Study sites are located in the Adelaide hills with always one burn and one adjacent control site respectively in Kersbrook Native Forest, Millbrook Reservoir, Para Wirra Recreation Park and South Para Reservoir. Some parts of the study sites in Kersbrook and Millbrook were affected by the Sampson Flat Bushfire. Affected sites are used to compare the effects on orchid pollinators after prescribed burns in contrast to wild fires.

Potential orchid pollinators are being identified using DNA barcoding with the mitochondrial cytochrome oxidase I (COI) gene. Sequencing results will be compared with existing databanks and confirmed using morphological identification. As the data accumulates it will build up a reference library of COI barcodes for the species found in the surveys.

The outcome of this research project might help to advise the optimal management of orchid species under fire-managed regimes in the Mount Lofty region of South Australia, as well as more generally in south eastern Australia.

160219 Anita Marquart Melangyna collatus on Caladenia rigida

A hoverfly, Melangyna collatus on Arachnorchis rigida syn Caldenia rigida (Rigid White Spider Orchid)

 

Orchids and their pollinators

Native bees, thyninne wasps and Syrphid flies are known orchid pollinators of South Australian orchid species. Orchids of main interest for this study were Caladenia rigida, Caladenia behrii, Caladenia tentaculata and Glossodia major. Caladenia tentaculata and C. behrii are sexually deceptive orchids and are known to be pollinated by thynnine wasps (Bates 2011). In contrast, C. rigida is food advertising and uses a broad range of bee and fly species, such as native bees and hoverflies (Faast et al. 2009). Glossodia major is a generalist in its pollination strategy and is using small native bees of several genera (Bates 2011, personal observations).

Preliminary findings

Syrphid flies were successfully separated into different species using DNA barcoding methods. Results show that we have two dominating species on our field sites in the Adelaide hills. Both species, Melangyna collatus and Symosyrphus grandicornis are common native Australian species. Both species were caught with orchid pollinia attached and were observed on Caladenia rigida flowers.

First findings suggest that hoverflies don’t seem to be much affected by prescribed burns or bushfires. Syrphid fly numbers vary greatly between the years of sampling, but we did not find a significant impact of prescribed burning or the Samson Flat bushfire.

Statistical analyses for the data on syrphids, native bees and thynnine wasps are currently underway.

Preliminary findings suggest that a range of pollinators are still present on field sites after prescribed burns and even after bushfires. Nevertheless, some specific species might be more sensitive to fires and might have disappeared from the study sites. For example, orchids relying on one species of wasp could be more affected by changes in the abundance of their pollinator after fire, than orchids that are pollinated by a number of different insects.

We will have to analyse our results in more detail to look into the specific species composition for the insect families, especially for native bees and thynnines, rather than looking at overall abundance.

160219 Anita Marquart Melangyna collatus with pollinia

Hoverfly, Melangyna collatus with orchid pollinia attached

References:

Faast R, Farrington L, Facelli JM, Austin AD (2009). Bees and white spiders: unravelling the pollination syndrome of Caladenia rigida (Orchidaceae). Australian Journal of Botany 57, 315–325.

Bates, R. J. (2011). South Australia’s Native Orchids. Native Orchid Society of South Australia.

Orchid Pollination Strategy for Corunastylis littoralis (Part One of Two Parts)

Part One – Attracting Pollinators

Corunastylis littoralis (Photo: Colin Bower)In 2015 a paper was published in the Journal of Plant Systematics Telopea (Vol 18:43-55) titled “Reproductive success and pollination of the Tuncurry MidgeOrchid (Genoplesium littorale)(Orchidaceae) by Chloropid Flies “. Much of the same material had been published earlier in a consultancy report for UrbanGrowth NSW, under the title “Pollination of The Tuncurry Midge Orchid (Corunastylis littoralis) Amended June 2014″ Prepared by Colin C Bower PhD.

Because of their details, research papers can contain some very interesting facts of interest to a wide range of readers. This paper was no different. The aim of the paper was to identify the pollinator(s), how the attractant worked, confirm that C. littoralis was not autogamous (self-fertilizing) or apomictic (reproduction without pollination) and to assess the requirements & long-term viability of the pollinator.

The following summary notes have been drawn from both the research paper and the consultancy report.  Note that Corunastylis littoralis is a synonym of Genoplesium littorale.

One of the interesting issues discussed was the different types of pollination strategies employed by orchids. It is commonly accepted that about one third of orchids use deceptive practices to attract a pollinator whereby they promise but don’t deliver. Some of these strategies are quite unusual. It would appear that there are at least four strategies now known. In order of frequency they are

  1. Food mimicry
  2. Sexual mimicry
  3. Brood-site mimicry
  4. Prey/carrion mimicry

The first two are well known to many orchid lovers. The orchid promises food such as nectar but does not produce any nectar or it has the appearance and even odour of the female insect pollinator so that it fools the male. The lesser known deception is brood-site mimicry where the female insect pollinator is tricked into laying the eggs on the flower but there is no chance for survival of the off-spring. Finally the most uncommon and unusual deception of prey or carrion mimicry, known as kleptomyiophily.

This method was discussed in detail in the report and made for fascinating reading although it was helpful to have a dictionary on hand.

Some insects are kleptoparasitic that is they feed on the haemolymph (roughly similar to blood) but from freshly killed insects. The researchers established that the pollinator for C. littoralis was not Drosophilidae (vinegar fly) but were instead from the families Chloropidae and Milichiidae known kleptoparasitic flies.

It has been observed that the pollinators swarm around the Corunastylis. This is a known behavioural pattern of kleptoparasitic flies that are attracted to the prey of other predators such as spiders, robber flies and other predatory insects.

It was noted that the pollinators were dominated by females. This precludes sexual deception and suggests that the females may require the haemolymph, which is protein rich, for egg maturation. It was also noted that C littoralis is a nectar producing orchid. It was considered that the nectar contained properties that mimic haemolymph.

Based upon these observations it was hypothesized that prey mimicry pollination syndrome was the best fit for the Corunastylis. Though this syndrome has been observed in orchids in the northern hemisphere, this would be the first time that this has been demonstrated as a possibility for Australian orchids.

Photo: Colin Bower

Photo: Colin Bower

Part two will consider the fourth aim of the paper which was to determine the method of reproduction.

Thank you to Colin Bower for checking this post and for allowing the use of his photographs.

 

Greenhood Pollination Strategy

Since orchids, and Australian orchids in particular, first came to the attention of the western world in the 1800s researchers have been fascinated by the so many different aspects of the orchid’s morphology and life cycle. One area of interest has been that of how orchids are pollinated. The mechanism of pollination has not always been clear as the orchids seem to use different and complex methods.  From time to time various papers have been published of observations by researchers.

One such paper was published in the Annals of Botany 113: 629 – 641, 2014 titled ‘Caught in the act: pollination of sexually deceptive trap-flowers by fungus gnats in Pterostylis (Orchidaceae)’ by R D Phillips, D Scaccabarozzi, B A Retter, C Hayes, G Brown, K W Dixon and R Peakall.

The ‘question and answer’ style of the paper helps with ease of reading and is worthwhile perusing, even for the lay person. The accompanying VIDEO is also of interest.

The essence of the paper was to establish whether sexual deception was used to facilitate pollination.  The species researched was Pterostylis sanguinea (syn. Urochilus sanguineus) and the researchers confirmed that this did happen.  Their research showed that the attraction for the insect came only from the labellum which exuded an alluring chemical.  P. sanguinea has a mobile hinged labellum which is a feature of other sexually deceptive orchids such Paracaleana, Caleana, Arachnorchis.

Urochilus sanguineus RWL

Pterostylis sanguinea syn. Urochilus sanguineus with the untriggered labellum

Urochilus sanguineus RWL(1)

Pterostylis sanginea syn. Urochilus sangineus with a side view of the labellum

 

2014 November Photograph Competition Part 2

Part Two of the November competition consisted of photographs of insects on orchids. There was quite a range of insects but the winner was a draw between Cyrtostylis robusta (Winter Gnat Orchid) with an ant and Pterostylis curta (Blunt Greenhood) with a midge fly; both taken by Doug Castle.

With today’s technology it is not only easier to take crisp images but fine details can be seen particularly when enlarging the image. Hence when the pictures are enlarged it is possible to see hairs on the ant and feathered antennae on the midge fly.

With identifying orchids, it is often the detail that is important. Both of these orchids are distinctive and can be readily identified but it is good to examine why this is the case.

Pterostylis curta (Blunt Greenhood)

Pterostylis curta (Blunt Greenhood)

With the greenhood, there is enough detail to see that the dorsal sepal and lateral petals have united to form a galea, ie hood, and that the lateral sepals are semi-fused and erect resulting in lateral orifices (side gap) between the two structures. These are some of the features that separate Pterostylis* from the other greenhoods such as Diplodium, Speculantha and Taurantha. This becomes apparent when browsing through the greenhood photographs, pages 286 to 339, in Jones “A Complete Guide to Native Orchids of Australia”. Having established that the plant is a Pterostylis, the twisted labellum is diagnostic of a P. curta as it is the only one that is described with a twisted labellum. Although not all the identifying features are present, enough information is available in this picture for identification.

In contrast the photograph of the Cyrtostylis robusta only has sufficient data to confidently identify it as a Cyrtostylis species, having a distinctive labellum that is larger than the lateral sepals and petals. In South Australia there are only two species and according to Bates (2011), the distinguishing features between the two

Cyrtostylis robusta (Winter Gnat Orchid)

Cyrtostylis robusta (Winter Gnat Orchid)

appear to be the leaf, the bud and the labellum. In this picture, the angle of the image does not give a clear view of the labellum (it could possibly be damaged) and of course there is no bud or leaf. It is possible that the pale edges of the dorsal sepal may give a clue to species identification as C. reniformis has mainly darker buds than C. robusta. Obviously Doug was able to identify it from his observations of the other features not present in this photograph.

In summary, one image is not always sufficient for identification. As was discussed on the night, to confirm identification, orchids should always be photographed from more than one angle, including pictures of other parts of the plant.

*In South Australia, Pterostylis foliata is a possible exception as it has no obvious lateral orifice.

References

Jones, D.L., T. Hopley, S.M. Duffy, K.J. Richards, M.A. Clements & X. Zhang (2006) Australian orchid genera. An information and identification system. CSIRO Publishing: Collingwood, Vic.

Bates, R.J. (2011) South Australia’s Native Orchids. DVD-ROM. Native Orchid Society of South Australia Inc.: Adelaide.

Jones, D.L. (2006) A complete guide to native orchids of Australia, including the island territories. New Holland Publishers: Sydney.

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.