I’ve recently noticed some clubtail dragonflies landing on a dock all facing the same way as other dragonflies that are on the dock. The cardinal direction faced varies so it doesn’t seem connected to something like sun position. More like if the first dragonfly faces a certain direction, subsequent ones landing nearby will also face that direction. Anyone have ideas about this behavior?
Insects whose larvae develop in water are often highly sensitive to the polarisation of light reflected off a water surface. It varies throughout the day and the sun can be hidden by cloud without affecting this ability. This article talks about this phenomenon called polarotaxis. It is possible that aligning with a certain degree of polarisation is most comfortable for a whole taxon, and your dragonflies may end up facing the same way without direct reference to each other. It would be interesting to note if they tend to settle facing along their flight approach vector, because flying towards the water at the same angle may be another reason for their alignment. Any insectophile want to comment?@Ajott
Does the orientation vary with the intensity of the sun? I have seen dragonflies landing and pointing their body almost directly towards the sun on hot middays, apparently to reduce the solar warming they experience.
My understanding is that dragonflies at risk of heat torpor from perching in the sun will seek shelter from it in shade. As they approach this threshold, they will perch higher off the ground, and/or adopt an ‘obelisk’ posture, with the tip of their abdomen pointed towards the sun. This article goes into lots of cool detail about dragonfly thermal regulation.
The title of this thread is Dragonfly Perching/Landing Orientation. Today I Learned that there is a whole Wikipedia article about obelisk posture!
Sun orientation was my first thought but then there were two separate groups of landings within minutes of each other that oriented in different directions.