Friday, June 18, 2010

Slaty Skimmer (Libellula incesta)

Libellula incesta doesn't seem to be as common in this area as its other skimmer relatives. I spotted only a few last year and haven't seen very many so far this season. Perhaps this is because these dragonflies prefer to perch over the water on rushes and other emergent vegetation rather than the shoreline shrubs. While many of its kin have rather stout chunky bodies the Slaty Skimmer is somewhat long in the abdomen for a skimmer and proportioned more like a pondhawk. This male is about 55 mm in length.

Note the position or bearing of the dragonfly's two front legs just behind its compound eyes, while it perches only on the remaining four. I've gone back through my image files and noticed other dragonflies in this pose ... is there a reason for this?

Slaty Skimmers are very active insects, alert, wary and difficult to approach. Like many dragonflies this one "obelisked" if it felt threatened. It's unlikely that it was thermoregulating because it seemed to react to my presence ... the closer I brought the camera, the higher it elevated its abdomen.

Skimmers tend to have preferred perches, so if the dragonfly takes flight it will in time often return to a favoured spot. It also seemed easier to approach these insects from above or behind. Nonetheless it took a considerable amount of time and patience to acquire these few photos.

The next two pictures were taken over a month later on July 29th. This male was missing a piece from the forewing on its far side. It was relatively fearless and docile (for a Slaty Skimmer), providing a good opportunity for some closeup shots.

Younger versions of the Slaty Skimmer appear quite different than the fully mature adults. The thorax has a cream-colored dorsal stripe and similarly colored sides. This is a teneral male ...

... and here's an immature female. Note the darkening toward the wingtips. Both of these immature dragonflies were found foraging in fields of weeds, wildflowers and shrubs, though not very far from water.