Tuesday, April 3, 2012

I-spied an orchid

On Sunday a plant hunt on Samphire Hoe beckoned.

If you don't know, Samphire Hoe is an entirely new (1990s) tract of land made with the chalky spoil from the Channel Tunnel diggings, which was deposited in front of the white cliffs between Dover & Folkestone. This not only provided the tunnel diggers with somewhere to dump the spoil but gave them an extra work base during operations. (The leaflet (pdf) for the site is available for download here.)

Along the path parallel to the railway we soon found ourselves looking down at our quarry; a diminutive early spider orchid (Ophrys sphegodes). (I reckon the grid reference to be about TR 28714 38902.)


Ophrys sphegodes is a really cute little orchid. To give you a sense of how little this particular plant is, here it is dwarfed by my Kent Library Card (which is the size of a credit card).


Further down the path we found another flower just opening.


The flower has yellowy-green sepals and a maroon-purple lip with distinct markings on it. These markings are called the mirror or speculum. In early spiders the speculum is usually H shaped, which you can sort of see below.


Why is it called an early spider orchid? Well it's an orchid and it flowers early; the early tag distinguishing it from the later flowering late spider orchid (Ophrys fuciflora). But why spider? Perhaps the speculum markings are evocative of a spider's abdomen? I'm not convinced. Ophrys is derived from the Latin for eyebrow and sphegodes means 'like a wasp'. Hmm.

Here's the same photo upturned into normal flowering position. It looks like a large maroon bee with a green waistcoat on.


A species of mining bee (Andrena nigroaenea) also think this flower looks like a bee. A girl bee to be precise. The orchid flower not only looks like a girl bee, and feels like a girl bee (girl bees are hairy) but it also smells like a girl bee (to male bees that is). The orchid's scent mimics 'odour of girl mining bee sex pheromone'. The male bees are enticed to 'copulate' with the orchid flowers (called pseudocopulation) which pollinates the flower. Job done :-)

Even more amazingly, after being pollinated the orchid changes it's scent to the pheromone released by an impregnated female mining bee viz. 'I'm an pregnant female so don't bother to try and copulate with me thank you so very much'. Incredible! (There's more detail in an article here and some original research here but only the abstract is available without paying a hefty fee (boohiss to paywalls)).

Here's the orchid dupe; Andrena nigroaenea (from Wikipedia)


The BSBI (Botanical Society of the British Isles) distribution map for this species is here. In the UK early spiders are confined to the limestone and chalk in Dorset, Sussex and Kent. They declined rapidly before 1930 as downland was ploughed up and today are classified as nationally rare. But although 'rare' and at the northern edge of their European range in the UK, at some sites there are substantial populations. The creation of Samphire Hoe offered suitable habitat and the orchid colonised rapidly. The Hoe now supports a vast population (in the tens of thousands I believe) of early spiders. It's well worth a visit in mid-April.

That the early spiders are in flower earlier than usual this year is unsurprising since we've had a lovely sunny spring. Recent research by scientists at Kew found (by comparing herbarium specimens to recent field observaitions) that for each degree increase above average spring temperatures, the orchids came into flower about 6 days early.

All in all a fascinating little plant :-)

Other Ophrys species I've seen in the last year include; this late spider orchid (Ophrys fuciflora) on the downs above Folkestone.


Bee orchid (Ophrys apifera), this one growing in Bedfordshire last summer.


Fly orchid (Ophrys insectifera) photographed at Yockletts Bank in Kent last summer on a dark, exceptionally wet day.


And finally (what I believe to be) a sombre bee orchid (Ophrys fusca) found growing by a roadside in Andalucia last month.


Further Information
ARKive is a fabulous online resource and has a picture of an Andrena bee pollinating an early spider ochid here
Kew have also published an article about Ophrys orchids and sexual mimicry here
Here's an Orchid Wiki page. 
Access to Samphire Hoe is off the west-bound A20 from Dover to Folkestone. Car-parking is pay & display - I believe currently £2 for 2 hours & over. There's a small visitor centre and they sell ice creams.

3 comments:

  1. Interesting stuff.

    I've seen Andrena nigroaenea but I don't think there are spider orchids - early or late - on the Isle of Wight.

    ReplyDelete
  2. This comment has been removed by the author.

    ReplyDelete
  3. Good morning Rob.
    I've found this ref
    http://www.hantsplants.org.uk/docs/Flora%20News%20Autumn%201992.pdf
    Under the heading Rumours & Truths p.3 it reports that an early spider was found on the IoW in about 1992. It doesn't say where.
    BTW we also have false widows in the courtyard (and one in the bathroom) here!!

    ReplyDelete