This time of year, at least around Denver, dragonfly like insects are numerous and visible. They ferociously guard their territories during the day and zip around catching insects around sunset. But which ones are actual dragonflies and which are their close relation, the damselflies? I get this this question a lot so I’d figured I’d put it here.
Actually there is an easy trick to telling the two apart. Dragonflies rest with their wings extended while damsel flies rest with the wings held fold over their back.
So there you go. All done. But while we are on the topic, neither dragonflies nor damsel flies are really flies. Flies are, technically speaking, insects in the order Diptera while dragonflies and damselflies are in the order Odonata, and entomologist commonly refer to them as odonates. Odonata is an evolutionarily old insect order, some of the first insects with wings were ancient dragonflies. In fact giant dragonflies are thought to have co-existed with dinosaurs. This piece from National Geographic covers two the theories about what they were so big. Just think about the nymph being the size of a house cat and attacking things underwater!
Despite being evolutionarily old, odonates are exceptionally good fliers. The can move all four wings independently and fly backwards, unusual in insects, and they have amazing eyes that can track individual prey. In fact, dragonflies catch over 95% of the prey they hunt. Watch one closely next time you see it flying around.
Male odonates often have hunting and breeding territories over water. Those with the best territories attract the most mates. But this can be rather complicated as the odonates have somewhat unusual and specific mating techniques where the male has to get the end of his abdomen in the correct position behind the females head. The female then lays eggs in the water.
As I’ve talked about before, juvenile insects don’t always look like the adults, and this is certainly true of the Odonata insects. Juvenile dragonflies/damselflies are called nymphs, and they live in the water. This picture from Bug Guide give a pretty got idea of what they look like.
Just like the adults, these nymphs eat other insects and small animals. They have a lower jaw that can extend rapidly to snag things swimming by. Although I don’t have a video of this, there are some on youtube. I like this one because it catches a fish! And this one because it includes some slow motion video so you can see the jaw extend. Crazy, right?
You can find these guys by turning over rocks in shallow rapids. There are other things that look similar (mayfly and stonefly nymphs) so if you really want to be sure, you have to get a look at the cool extending mouthpart. When it’s not extended, it looks like a shield guarding it’s neck.
Happy bug hunting!