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.