Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Sunday, January 23, 2011

Wasp Orchid - Chiloglottis reflexa - comes into flower

This group of "Short-clubbed Wasp Orchids" (Chiloglottis reflexa) is flowering right on the edge of one of the local roads in Kangaloon. Alan Stephenson spotted them when we were out admiring a large clump of Hyacinth Orchids, nearby. 

Look for the paired leaves on the ground. 
There are two open flowers and two buds visible.
They are small plants and even smaller flowers, 
as made evident by the scale of Alan's camera lens.
(Click to see the flowers)
Wasp Orchids - in situ - in leaf litter
 Here are two of these flowers together.
As plants which grow in colonies, it is quite common to get
two or more flowers together in a single image.
Chiloglottis reflexa - a pair of these tiny flowers
The "insectiform callus" (gland in the shape of an insect) covers most of the labellum of the flower. 
In other species the shape or position of the callus is different.
(Click to enlarge image)
Chiloglottis reflexa

These plants get their name "Wasp Orchids" from the "callus" - the glands on the labellum which resemble the body of a female wasp. They are part of a large group of Orchids which employ what is termed "sexual deception", to induce male wasps to attempt copulation with the flower, in order to achieve their own pollination (the Orchids that is). It used be referred to as "pseudo-copulation", but that term has gone out of favour in this more politically correct age. The technical people who have studied this phenomenon say it is both a visual trick and a scent based mimicry of the pheromones of female wasps.
The reflexed "Lateral Sepals" are clearly visible beneath the labellum.

A detailed look shows two points of note.
  1. There is a pair of Aphids (adult and nymph) on the stem of the Orchid.
  2. More unusually, the petal on the near side of the flower is showing some aberrant growth of calli (glands) which is normally restricted to the labellum only. The petal is reflexed down against the stem in its mature position (once the flower has opened). But in the development of the flower, the petal is adjacent to the labellum (which botanically is simply a modified petal). So the fact that some of the glandular development has crossed over to the lateral petal is not entirely surprising. But it is the first time I have seen this occur.
 Aberrant "callus" growth on the reflexed petal - that is unusual. Two Aphids.
This over-exposed photo (accidental I assure you) serves almost as an X-ray to highlight the shape of the head of the insectiform callus. Different members of this and related genera have different shaped "heads" or "necks" to these glands. So, although the image is weird, it is actually quite useful. In this case the head is clearly heart-shaped when seen from the front of the flower.

(Click to enlarge)
Accidental over-exposed image, but it shows well the shape of the "head" of the callus
That heart-shaped head of the insectiform callus is clearly visible in right hand image in the botanical illustration, from PlantNET.
Illustration from PlantNET - for Chiloglottis reflexa.
This is the first of the summer/autumn flowered Chiloglottis which I have seen this season. Something to look out for, obviously. They are most easily seen by looking for the mid-green, flat leaves, in opposite pairs (growing away from eachother) on the ground. Once you see one, there are usually more around, as they tend to grow in colonies. These plants were growing in loose grey sandy soil, over sandstone, within a Eucalypt forest.

7 comments:

Anonymous said...

Great photo, wish I could have been there, I have never seen an insectiform look so much like a live insect
Kirsten

Denis Wilson said...

Hi Kirsten
I assume you are referring to the accidentally over-exposed image. Interesting, eh? Next best thing to an X-Ray.
Anyway, these are just starting to flower - so plenty of time to see them in the flesh. Another species - Chiloglottis sylvestris - is budding up, so plenty to see over the next few weeks. That one is good because not only is it on its southern limit here in Robertson, we also have an alba form (green flowers - no pigment) on one side of the road, and normal (reddish) ones on the other side of the road. Convenient, eh?
Cheers
Denis

Prem Subrahmanyam said...

I bet the petal showing some of the calli normally seen on only the lip is not due to proximity between the two during development, but rather a dash of pelorism...i.e. the petal followed some of the 'rules' that the lip would normally follow during development. This is the same phenomenon seen in 'splash petal' Cattleyas.

---Prem
The Florida Native Orchid Blogger

Denis Wilson said...

Thanks Prem.
I was not aware of the term, "pelorism", but I was trying to suggest the plant got its instructions "confused", by noting that the Labellum is really a petal, so another petal beside it getting the same "instruction" (to grow calli) is not that surprising.
Thanks for the reference to "pelorism". I shall check it out further. Much appreciated.
Interestingly, there is some history for this, in this genus, because the "type specimen" for Chiloglottis trilabra was named from specimens with "three labellums" Jones, D
Having read that comment ages ago, when I saw my photo I wondered if that was a reference to the same phenomenon? After all, I only photographed that plant from one side. Maybe the other side has it too. I need to go back and check.
Thanks very much for the comment. Great stuff to learn things from experienced people such as yourself.
Denis

Mr. Smiley said...

Denis
Wonderful. Most informative.
DR

Denis Wilson said...

Thanks Dave
Glad you liked that post.
I put in a katydid on my Lilium from yesterday - just for you (bit I didn't say so).
A very ordinary Katydid, if there is such a thing!
Cheers
Denis

Le Loup said...

Good one.
http://woodsrunnersdiary.blogspot.com/