Damselfly Nymph

2009 August 1

At the same time as we caught the dragonfly nymph, S_ also caught a number of these fragile-looking fellows. I thought at first they were something like, oh, maybe some sort of mayfly. So we put about a half-dozen of them in a jar, took them home, and . . . by the time we got them home, there were, er, noticeably fewer of them. Then we saw that one was eating one of the others, and we realized that these were no gentle detrivores, but some sort of active hunter. Unfortunately, they were of fragile constitution and the ones that hadn’t been eaten had died by the time I had the opportunity to take pictures, so I pulled one out of the water to photograph on the macro stage.

Given the fact that they were clearly carnivorous, we quickly realized that they were actually damselfly nymphs. Damselflies are related to dragonflies, except that they are much smaller. And, instead of having internal gills like dragonfly nymphs do, damselfly nymphs have external gills at the tip of the abdomen, that open up like the petals of a flower in the water (but unfortunately lay flat when they are in the air).


You can see the buds where the wings are developing under the skin in this next picture. Once it matures, the damselfly will haul itself up on a reed stem or similar object, split open its skin, and emerge as an adult damselfly.


And when we look at the underside, remember how the dragonfly nymph had an extensible lower lip that it could shoot out to grab prey? Well, it looks like the damselfly nymph has one that is even bigger in proportion to its body. In this picture, it is unfolded and extends all down its underside:


I’m not sure if there are claspers at the tip, the damselfly lip ends in something that looks like a scoop, or maybe a pouch. This might be better suited for scooping up smaller prey.


Although the lip looks good for catching tiny prey, they are also certainly capable of eating prey about as large as themselves (like, say, each other), so the lip-scoop must be pretty effective for a wide range of sizes. One thing we did notice was that, while damselfy nymphs were very common in the pond we found them in, we did not see a single mosquito larva. Not one. Even though it was the exact kind of semi-stagnant pond that mosquitos normally love. This is very suggestive about what damselfly nymphs normally eat, don’t you think?

2 Responses
  1. August 7, 2009

    What an outstanding bit of detective work! What surprises me is that they didn’t survive the trip home. I wouldn’t think they’d be so fragile. The scoop is pretty alarming, too. Such a violent world these insects live in.

  2. August 7, 2009

    Yes, we didn’t expect them to be so fragile, either. As for the lip-scoop, this was another case where I didn’t have any idea what I was photographing until I got the picture onto the computer and could look at it full-size. The feature wasn’t even visible on the camera’s LCD screen.

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