Odonate of the week: Celithemis eponina

I have accumulated a few photos of dragonflies and damselflies over the past few years and I don’t really have anywhere to share them, so I thought I would post them here.  Since it features in the header of the blog, I though I might as well start with this one of Celithemis eponina.  And yes, I did spend about 15 minutes trying to get the wings parallel to the top and bottom of the photo.  It’s a good job this is a percher, not a flier…

Celithemis eponina

In fact, having mentioned the difference between perchers and fliers, I might as well elaborate.  Phil Corbet distinguished dragonflies into two categories: (i) those that spend the majority of their time perching with occasional forays to chase food, mates or competitors (“perchers”), and (ii) those that spend the majority of their time on the wing and only resting occasionally (“fliers”) (Corbet, 1962; revisited by Corbet and May, 2008).  There has also been a suggestion that a similar dichotomy can be found in the damselflies (Zygoptera, which represent the “other half” of the order Odonata) (Paulson, 2004).  After careful scrutiny, it appears that the percher-flier dichotomy is a real phenomenon (although not a perfect system of classification) and is associated with variations in thermoregulation and morphology between species.  While perchers tend to regulate their body temperature by modifying their orientation in relation to the sun and moving in and out of shade, fliers generate their own heat during flight which they regulate by controlling the circulation of haemolymph through the body (haemolymph is analogous to blood).  Fliers tend to have morphological adaptations that permit long periods of flight.  These include more efficient wings (usually longer and thinner) and larger amounts of fat as an energy store.  Perchers, on the other hand, tend to convert fat to flight muscle which enables them to fly faster and more vigorously for shorter periods.

Most of the dragonfly photos you see that make you go “oooh” (and pretty much all of my good photos) are probably percher species.  The best way that I have heard to photograph fliers is to catch them (no mean feat in itself), chill them in the salad drawer of a refrigerator for a few hours, and then pose them on a well-lit piece of vegetation…  Cheating but effective!

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References

Corbet, P.S. (1962) A biology of dragonflies. Witherby, London.

Corbet, P.S. & May M.L. (2008) Fliers and perchers among Odonata: dichotomy or multidimensional continuum? A provisional reappraisal, International Journal of Odonatology, 11: 155-172.

Paulson, D.R. (2004) Why do some zygopterans (Odonata) perch with open wings? International Journal of Odonatology, 7: 505-515.

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