Wednesday, January 19, 2011

Damselfly nymph in winter

At the end of October I took a walk to Altona Marsh and collected some of the water along the track.

I just filled up two plastic peanut butter jars and made sure I had some duckweed, algae, sediment from the bottom and bits of other stuff. I didn’t really look to see what I had. With two jars I was sure to get something interesting.

Sure enough, after the water settled for a few hours I was able to see an Odonata nymph. The three leaf-shaped gills extending from the hind end of the body indicates that it is a damselfly. I haven’t a clue what species this is. They overwinter as nymphs and emerge in late spring. They are very predacious and eat every kind of aquatic insect, small crustaceans and snails so I think there will be plenty of food in this one jar for a while. I have actually seen a few things disappear since March and I suspect this is the culprit. Most of the time it just sits and waits for a victim to come by.

I soon realized that I was going to get distorted photos from the jar so I bought a small rectangular plastic tank which made it easier to get close up with my camera. Just recently I took the photo below. I think it must have molted because it is so clear and you can see the insides. Earlier it was emerald green. They molt between 6-15 times. With each instar the nymph get darker in color. Now you can clearly see the tracheal gills and tracheae and lines with the consequent flowing of the blood throughout. I think the darker part in the middle is its heart.

You might be able to make out the labium that looks like its chin. When it is ready to catch something the labium flies out with the swiftness of a frogs tongue and grabs it’s pray and snaps it back into its mouth. I watched it stick part of it out and place its front legs up as though it were cleaning the tip. I wasn't quick enought to get a photo but here is another view.

When I turned the container around it would bend its body to move the tail in my direction. I wonder if that was some sort of defense action. It did it several times.

They move about slowly by crawling or swaying like a fish by sweeping their tail from side to side. It has been really fun to watch especially as the snow falls.

Check out other blogs about water at Watery Wednesday.


Woodswalker said...

That is amazing! A great project to keep in mind for next year, when the ice unfreezes.

squirrel said...

Jackie it has been a lot of fun. I hope to post more about what I have been finding in that jar. From Plenara to liverworts are living in the water. Thanks for your nice comment.

Jessica said...

Very cool picture! Thanks for sharing.

Magical Mystical Teacher said...


Water as river or puddle or frost;
Water that’s roaming alone and seems lost;
Water that looks like sharp daggers of ice;
Water that’s frozen as small as white rice;
All of this water, no matter where found
Will one day seep back far, far underground
And surface again for fountain and flush—
Water, ah, water, you make things so lush!

© 2010 by Magical Mystical Teacher

Roiling River

Ted C. MacRae said...

The last photo is awesome!