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Dragonfly Wrappers – A fine pair of Exuvia!!

Discussion in 'Exhibition Lounge' started by John_Baker, Jun 7, 2011.

  1. John_Baker

    John_Baker Well-Known Member

    After the BDS meet Adrian Harris and I went over to Knightshayes Court which is a wonderful Victorian country house with richly decorated interiors and a magnificent garden - owned by the National Trust, located near Tiverton possibly one of their nicest properties. In the garden is a big ornamental pond full of various lilies, the place was alive with damselflies and around 20 dragonfly exuvia, which is their larvae stage or how they exist before changing into the final more familiar flying form. A couple of family snaps, meet the gang…

    1 - smile at the camera...

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    2- a top and bottom shot...

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    3 - Useful side shot showing the labium or mouth parts and relative size of the eyes. The white spiracle tubes are what the larva use to breath...

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    4 - final group shot...

    [​IMG]

    Ok there are plenty of other shots, I did some with a reversed 50mm, huge magnification. After checking the books (these are 44 & 45mm long) I believe these to be from Southern Hawkers, however, there was no sign of the adults anywhere...

    Just for MickLL here is the full shot of the Cordulegaster boltonii - as the longest dragon in the UK they are a total pain to get with a full frame shot, not helped by them nearly always being either in flight or hanging off bushes which do not make for great images.

    [​IMG]

    If you are visiting in the Tiverton area, I would really recommend Knightshayes Court as a site well worth a visit...
     
  2. Rustyknight

    Rustyknight Well-Known Member

    Lovely finds John. I'm glad you mentioned the white tubes, and their use, as I was baffled as to what they were.
     
  3. OneTen

    OneTen 'Two Breakfasts'

    Very interesting John and great timing as I joined the BDS yesterday.

    I know Knightshayes very well, I did my NT Dangerous Trees course there.
     
  4. GDN

    GDN Well-Known Member

    Very nice John.

    Do you find these next to the water? in the water? on reeds? Just wondering as I've never yet seen any pre-dragonfly larvae (other than what we (the kids and me) pulled out of the ponds with nets). :)
     
  5. John_Baker

    John_Baker Well-Known Member

    Richard - BDS for £15 per year is a great deal, the thing I love about the field trips is they are normally filled with interesting people who have very separate areas of specialist form birds, through plants and everything in between the other great advantage is having lots of pairs of eyes to look – dragons are still not easy to find. I hope you have an active group where you are!

    Hi Mike, they are connected to the rear end of the beast...

    Hi Gary, Damselflies tend not to go too far from water, climbing up reeds and stems and emerging there. Dragons can also do that, but occasionally they will go for a bit of trek before climbing and going through the process. I saw a Downy Emerald emergence about 10 meters from the waters edge. Due to the ornamental nature of the Knightshayes pond there were about 20 exuvia Souther Hawker exuvia all over the reeds.

    Here is one of the above in situ - they are very light and brittle, I have a box of them at home, much to Mrs B's annoyance!!!

    [​IMG]

    Here are a couple of emergence shots - taken last year when I was made redundant had a lot more time to spend out and about with the camera

    [​IMG]


    This is possibly one of my all time favourites taken with the G - the body of this one is yet to fill out - I have posted these before but they show how it all works...

    [​IMG]
     
  6. MickLL

    MickLL Well-Known Member

    Thanks John,

    I enjoyed those a lot.

    [extreme pedant mode] When the larvae live underwater they have exoskeletons (external skeletons) and, in common with most species with exoskeletons cast off the small one as they grow and develop a bigger one. The exuvia is simply the final larval exoskeleton before transformation into the flying insect.

    I have always known the white tubes as trachea rather than spiracle tubes. No-one quite understands the full respiration story of the larva but they seem to have gill like structures (sometimes in the anus!) and the white tubes are used in the larval stage. As you probably know insects 'breathe' by a process of osmosis through holes/tubes called spiracles - but that applies to the land insect only - spiracles don't work under water for dragonflies therefore calling them spiracle tubes seems to be a misnomer.

    Could your exuvia be of the hairy dragonfly? There is a population apparently near Tiverton and the picture puts me in mind of the hairy.

    Finally dragonfly larvae are actually nymphs (look it up!) but dragonfly people always call them larvae - even in the learned literature. Quite why I don't know. [/extreme pedant]

    Sorry to have bored you . Thanks again for the pictures. As you can see I found them very interesting.

    MickLL
     
  7. John_Baker

    John_Baker Well-Known Member

    No trouble, the problem was me trying to simplify things to a certain extent without boring people silly – never easy and always creates as many problems as you try to solve.

    I did check out my thoughts with Dave Smallshire (my local Guru), my main reference points:
    Length – Hairy 34/40mm Southern 38/48mm - Specimens were around 44/45mm
    Head characteristics – Hairy, eye small compared to head about 1/3 of depth, Southern eye about 1/2 head.
    Labium – Hairy ratio length to width around 3:1, Southern much longer at 4:1

    I was using Dave’s updated book as my reference “Britain's Dragonflies: A Field Guide to the Damselflies and Dragonflies of Britain and Ireland” see http://www.nhbs.com/britains_dragonflies_tefno_117057.html
    This is an updated volume with a couple of new sections, a great bit on both vagrants and potential vagrants and an enlarged section on larvae and exuviae – a good read for anyone with an interest in the subject.

    I was keen to get the ID right as I need to report these to the BDS as a new recording for the site – not that it is a new species, just there are no national records.
     
  8. Steve52

    Steve52 Well-Known Member

    Great pics as usual John. Have you thought of providing these pictures (and others) to local schools/colleges? I'm sure they would make wonderful teaching aids.
     
  9. MickLL

    MickLL Well-Known Member

    Thanks once more. It's quite hard with exuviae and I'm far from being an expert.

    I've been recording sightings with the BDS recently and as a result I've got to know the recorder for Kent and she's taught me a lot and taken me to some great places.

    MickLL
     
  10. Steve52

    Steve52 Well-Known Member

    I assume she's taught you a lot about dragonflies etc and places to see them!:D:D:D
     
  11. MickLL

    MickLL Well-Known Member

    At my age (and hers) I promise you that's all you would want!

    MickLL
     
  12. geoid

    geoid Well-Known Member

    Really good photos. Still in the North West, all I've seen are the small may-flies, and that's it!!!

    This is all a bit quatermass and the pit isn't it? Lol:cool:
     

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