Insect in the spotlight: Darting Dragonflies

Since starting this series, I wanted to photograph a dragonfly. However, every time I saw one, it quickly flew away and I started giving up hope of photographing one this past season.  So to my surprise, a little over 3 months ago I finally had the opportunity to photograph not just one, but two different dragonflies.

The first one was sunbathing on a lounge chair in my garden. I spent a lot of time trying to figure out which species and gender this is, but it has proven to be very difficult. It could be either a Vagrant Darter (Sympetrum vulgatum) or a Common Darter (Sympetrum striolatum). And it is either a young male or a female. Older males have a reddish or reddish-brown color which would make it easier to determine which species it is. Females are less brightly colored like the specimen below, but should be recognisable by a anatomical structure at the tail, which is used for laying eggs. Young males are recognisable by their genitalia which are located at the abdominal region close to the wings. In the pictures I took, I couldn’t see either structure. Another trait that is used to distinguish between the two species, is a by a black line between the eyes. Unfortunately I do not have pictures of other perspectives, so it’ll probably remain a mystery which species and gender this particular sunbather is.

The next day I found a different dragonfly relaxing near the butterfly bush. This specimen was slightly easier to determine. It is a migrant Hawker (Aeshna mixta), possibly female or a young male.

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Dragonflies have remarkable lifestyles. Check out the videos below to learn more!

Short BBC documentary about the dragonfly life-cycle: 

How do dragonflies fly?

A dragonfly on the hunt:

 

Questions or comments are -as always- welcome!

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One thought on “Insect in the spotlight: Darting Dragonflies

  1. I liked watching the high-speed-camera flying video, to see how the dragonfly moves its wings.

    The essence of wings is to push the air down, so that you push yourself upward (basic physics: “action=reaction”). When you don’t move the wings, you need an incoming airflow (in this case: wind), and you need to rotate that airflow downwards. With a flat wing, you can only do that when the wing is a bit tilted (so the front is a bit higher than the rest)

    However, if you tilt the wing too much, the airflow “detaches” from the wing, and you lose the ability to push the air down; the consequence is that the wing “doesn’t work” anymore. In airplanes, this is called “stall”, and it has been a cause in several crashes. It might be different for insects though, since air behaves a bit different on such small scales.

    From this, I would expect that the front wing of a “gliding” dragonfly has the smallest angle of attack (“tilt”), and it sits a bit above the rear wing: this way, the airflow from the front wing would help to prevent stall on the rear wing, so the rear wing can have a larger angle of attack, to push the air even more downwards. Compare it with “slotted” flaps on aircraft wings.

    Watching the video again with this in mind, the front wing seems indeed to be above the rear wing, but it’s hard to say anything about the angle of attack. It looks like the wings are connected quite loosely to the dragonfly, so the angle of attack changes continuously.

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