Thursday 25 October 2018

Willow Emerald Damselfly - NEW Behaviour Observed?

I have spent the last few years spending countless hours watching, studying and photographing the Willow Emerald Damselflies of Nethergong and during this time, have managed to find out a few interesting aspects of their behaviour. A few years ago and still today, I have observed them ovipositing into Stinging Nettle stems which I believe was one of the first records of this happening in the UK. Yesterday was another one of those days where I observed some behaviour which I have never seen before. I often stand at the side of the stream and observe the Willow Emerald Damselflies on a couple of Alder trees opposite me and with this, have seen them ovipositing into the branches of the tree over the past few years. They often land on the catkins where normally they fly off deeper into cover to egg lay but yesterday was slightly different. I had decided to sit down opposite the Alder trees and have a drink and something to eat and was observing some pairs in tandem whilst males perched and rushed out every now and then to see of rival males. As I watched, I could see a pair of Willow Emerald Damselflies in tandem which landed on a catkin but this time, they stayed and the female curled round her abdomen and started to oviposit into the catkin itself. I have never seen this before despite watching them for many hours over the years and was intrigued if she was aware what she was egg laying in. They stayed for a few minutes where she clearly did egg lay and then both took off and remarkably landed on another catkin where again, she started to oviposit. Although not the best photos due to the stream being in between us, I managed a few useable shots showing the pair in tandem ovipositing into the catkins.
 
Willow Emerald Damselflies (Chalcolestes viridis) ovipositing into Alder Catkins
 
As I continued to observe the pair, I soon become aware of another pair which were also ovipositing into catkins. This then begs the question as to why are they doing this and are they clearly aware of their actions? My initial thoughts related to the catkins getting blown down of falling off the tree during the Winter or in the Spring which would then give the eggs inside a safe passage to the stream where they would then wash up providing a safe sanctuary for the eggs to then develop and emerge in the Spring. The newly emerging prolarva would then already be in the water giving them a better chance of survival. On returning home, I looked through some internet sites to see if I could find any information on this but despite a good search, I failed to find any information on the use of ovipositing into catkins by Willow Emerald Damselflies.  I contacted Adrian Parr from the British Dragonfly Society who kindly emailed me back me and said "Your discovery of individuals ovipositing into Alder catkins is pretty amazing, and I've certainly not come across this before, though I'll double check the literature". This all sounds very interesting and it could be that I have indeed stumbled across some new behaviour not really observed before. Despite it being quite late in the season for them but with some nice weather of late, I made an excellent count of 73 Willow Emerald Damselfly yesterday around the Nethergong site. Hopefully they might make it into November although the weekend temperatures are to quickly plummet so fingers crossed, this is not the last time I get to see and enjoy one of my favourite damselflies this year.
 
Willow Emerald Damselflies (Chalcolestes viridis) ovipositing into Alder Catkins


12 comments:

  1. Fantastic photos of the Willow Emerald Damselflies, lovely to watch.

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    1. Many thanks Bob. The photos aren't up to much at all but The story they show and tell could well be very valuable.

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  2. I wonder if the catkins have to be of a certain stage of maturity before they are attractive to the Willow Emeralds?

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    1. I don't know. Maybe they think they are branches but I suspect that it may be something to do with the feel of the catkin and that the female can oviposit into it well.

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  3. Hi Marc, My you have steady hands with all that excitement. Mike.

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    1. Many thanks Mike. Always nice once you've put the hours in to see some new behaviour. Still much to learn.

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  4. Congratulations on observing and documenting this truly amazing behaviour, Marc! Another feather in your cap!

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    1. Many thanks Richard. Great to observe something new and add a little more information about the lives of these damselflies.

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  5. Hi Marc.
    Your observation and discovery is wonderful, and that is down to the hours and dedication that you put in. Keep it up.

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    1. Many thanks for your kind words Ken. Much appreciated.There's still much to be learnt I suspect and it's always nice to get a small reward for your efforts.

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  6. Excellent observations of previously unknown behaviour Marc, and just reward for the many hours in the field that you put in. This behaviour could certainly assist in the dispersal along a watercourse as the catkins containing eggs drift off downstream anywhere that there is any significant sort of flow.

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    1. Many thanks Adrian. Good to hear from you. The catkins will open in the spring to pollinate themselves and then I assume fall off. I suppose they could then fall and some containing eggs may well them be helped to disperse downstream. All interesting stuff nonetheless.

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