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Archive for July 25, 2011

Dragonflies and Temperature Control

Often on hot, sunny days you will see dragonflies perched facing away from the sun, with their abdomens raised high in the air above them.  This position actually has a name – the obelisk posture – and some dragonflies and damselflies assume this position to prevent overheating.  They raise their abdomen  until its tip points at the sun, minimizing the surface area exposed to it.  The name given this posture comes from the fact that when the sun is directly overhead, the vertical alignment of the insect’s body suggests an obelisk. The meadowhawk dragonfly in the photograph  assumed  the obelisk posture several seconds after the sun came out from behind  the clouds.  As soon as the sun was obscured by clouds again, the dragonfly would lower its abdomen to a horizontal position. It continued doing this for a considerable amount of time.  Sometimes abdomens are raised for reasons other than temperature control, including threat displays during conflicts.