Tuesday, 16 January 2018

King of the Nymphs

During my net dipping sessions over the weekend, it was pleasing to be able to net a few Emperor Dragonfly nymphs of varying sizes. They ranged from the small stripy patterned nymphs through to the fully grown nymph which when placed next to each other, really demonstrated the size of this impressive nymph. Having reared a few Emperor nymphs over the past few years, they will eat almost anything and must rate as one of the top predators under the water. I remember observing a near fully grown individual attack and eat one of nearly the same size last year. Such is there appetite, they will take on their own kind. It was interesting to read that to avoid being predated by their own kind, the different sized nymphs operate on different plants and different depths, thus, hopefully avoiding each other. Having observed them at the weekend in the trays before releasing back into the water, I took a few photos which really didn't come out too well but knew I had a few files from last winter which had some photos I had not published before. Having found a few photos, I set about editing a few images which hopefully show off this species shape, features and markings well. Hopefully I can continue to seek out new dykes and ditches in the forthcoming weeks to monitor and see what species of dragonfly and damselfly nymph occur nearby.
 




Emperor Dragonfly Nymph

 


Sunday, 14 January 2018

First Dip of the Year

I decided yesterday and today to spend a few hours at Grove Ferry where as well as a bit of birding, the aim was to do a bit of net dipping in one of the dykes to see what dragonfly and damselfly nymphs could be found. I had made a few visits to this dyke last season where a good range of species were noted and I hoped that a few of them would use this ditch to breed in.

Grove Ferry Dyke

I spent an hour or so walking up and down the dyke and managed yesterday to find 3 Emperor Dragonfly nymph, 1 Hairy Dragonfly nymph and a few Azure / Blue tailed Damselflies. The surprise came when I netted a Hawker nymph which at first I thought could have been a Norfolk Hawker nymph but a quick scrutiny through the 10x hand lens to check the shape of the Epiproct and length of the Cerci revealed that this was a Migrant Hawker nymph.
 

Migrant Hawker Nymph
 
I have often wondered if I was to net a Norfolk Hawker nymph whether I could take photos of it in the tray and then publish them on my website and blog. I am aware that they are a protected species and mustn't be collected etc but surely, just taking photos on site and then returning it safely back to the water won't do any harm will it? I aim to return to this site on a number of occasions and may well at some point net one of these. I am also seeking permission hopefully to be able to walk on both sides of the dykes to search and collect a few exuviae as the season progresses. I would like to know others thoughts on this situation if possible as I wouldn't want to find myself in a wrong situation. I returned again this morning to Grove Ferry where after speaking to the local birders, I spent another hour netting in the dyke. I managed to find 2 Emperor Dragonfly nymph including 1 pretty much fully grown individual, 1 Hairy Dragonfly nymph and 1 Migrant Hawker nymph which was again checked as to make sure that it wasn't a Norfolk Hawker nymph.
 

Migrant Hawker Nymph
 
 Its interesting to read that the Migrant Hawker eggs don't hatch until early spring where they then develop rapidly and emerge after a few months. I have read that they cannot tolerate our cold waters in winter so why am I finding nymphs now for? I can only assume they didn't develop in enough time to emerge and so are seeing out the winter in order to emerge this year. Something else for me to research and see what answers I can find. Although no adults will be flying for a few months yet, its nice to get the season off to a start with a few nymph sessions. Roll on next weekend.
 
Migrant Hawker Nymph (showing Epiproct shape)
 


Monday, 8 January 2018

Caudal Lamellae Comparisons

One of the many interesting features of damselflies are the three caudal lamellae that protrude from the abdomen. These provide the primary means of respiration but also have many more functions to them as I have been learning recently and some findings have produced some interesting questions. The caudal lamellae provide in most cases a useful guide to identifying the species as most species have unique shapes and markings which when viewed up close, can help to aid identification. They are also used in defence sometimes to warn off other damselflies and I have also witnessed them underwater seemingly communicating with each other as they move them from side to side. Damselflies will also use them to escape danger quickly and using them as paddles, can quickly move out of danger at some speed. The use of them escaping has also caused a few questions for me in that with three caudal lamellae present, they can indeed move quickly out of danger but what happens if they lose any of these? I assume that whilst they can still swim away from danger, they will become prey more easily to other underwater insects. It also makes me wonder how the breathing is affected if the damselfly loses all three caudal lamellae as I have often found whilst pond dipping. Whilst I understand that they will grow back, this is an area for me to read further about on how they continue to successfully breathe. So as you can see, the caudal lamellae have a number of important functions and I have only scratched the surface on their importance to the lifecycle of a damselfly but I thought I would use this post to highlight some of the similarities and differences that can be seen in the Emeralds, namely the Common, Scarce and Willow Emerald Damselflies. Quite often the shape of the caudal lamellae can be a helpful clue to the species. Some show bands on them while others can show pointed or rounded tips. In the case of the female Emerald and Scarce emerald Damselfly, another aid to help identification is the length of the ovipositor. As can be seen in the photos, the ovipositor of the Scarce Emerald Damselfly reaches beyond S10 whereas the Emerald Damselfly does not.


Scarce Emerald Damselfly Exuviae (female)


Emerald Damselfly Exuviae (female)

 This feature can also be seen well in the adult female damselflies. In my studies of the female Willow Emerald Damselfly exuviae of which I have not seen that many photos on the internet and books, the ovipositor seems to also reach just beyond S10.

Willow Emerald Damselfly Exuviae (female)

There is no doubt still much to be learnt about their biology but I have found it fascinating looking back over some of the exuviae in my collection and enhancing my own knowledge. This will I'm sure give me a few more excuses to look over, photograph and compare and publish a few more from my collection.


Saturday, 6 January 2018

Keeled Skimmer (Orthetrum coerulescens) Exuviae

During June last year, I made a trip to Hothfield Common near Ashford which hosts Kents only Keeled Skimmer colony. On arrival in warm sunny conditions, I made my way to the small area which has a boardwalk cutting through the boggy area. I had only been to this site once before but remembered that they often spent some time basking in the sunshine on the boardwalk, It wasn't long until I noticed a few males flying low over the bog and with patience, they soon flew in and landed on the boardwalk where I was able to obtain a few images. As well as seeing the dragonflies, I wanted to spend some time seeing if I could find an exuviae of this species as I didn't have one in my collection. I spent some time looking over the side of the boardwalk and in all honesty, I didn't expect to find any but after what seemed an age looking, I somehow found one very low down on some grasses. I carefully removed and potted up and on arrival home, checked some of the identification features to make sure this was indeed a Keeled Skimmer exuviae. I noted the almost straight labial mask with shallow serrations, small size, small eyes and the lack of spine on S8. Its taken me a while to get round to it but I spent a while this afternoon taking a few photos from different angles of the exuviae to hopefully show a few of the features. I always find it amazing that they emerge from the smallest of holes and then transform into amazing dragonflies. I have a few more exuviae still to photograph which I shall do and post in due coarse. On a different subject, I purchased the latest version of Photoshop yesterday so it may take me a while to get to grips with it and do the photos justice with my editing skills. I have been using Photoshop Elements 2 for a number of years now but it has served me well. These are my first attempts with the new software which seems quite different but hopefully with a bit of practice, I will get the hang of it.

Keeled Skimmer Exuviae (side view) 


Keeled Skimmer Exuviae (side view)  


Keeled Skimmer Exuviae (side view)  


Keeled Skimmer Exuviae (top view)  


Keeled Skimmer Exuviae (mask)  


Keeled Skimmer Exuviae (side view)  

Keeled Skimmer Exuviae (mask)