EPOW - Ecology Picture of the Week

Dragonfly (Trithemis tropicana), Family Libellulidae
Monkoto, Democratic Republic of Congo, Africa

Explanation:   This female skimmer dragonfly was putting on a show, striking at least these three specific postures in the morning tropical heat of equatorial Africa.  Why?  What was the purpose?

Dragonflies adjust their postures as a form of "behavioral thermoregulation" -- to regulate their body temperature.  

In the third photo in this sequence, this dragonfly has raised her abdomen to near-vertical and drooped her wings to provide shade to her thorax to minimize exposure to sunlight.  Dragonfly experts call this the "obelisk" posture.   

Other postures, however, may be less easy to explain.  Perhaps they adjust their wings for more aerodynamic reasons, or perhaps to display for territorial or mate-attraction purposes, although dragonflies tend to display in flight rather than on perch.  

 
Obelisk postures.
  

Information
    De Marco, P., A. O. Latini, and D. C. Resende.  2005.  Thermoregulatory constraints on behavior: patterns in a neotropical dragonfly assemblage.  Ecology, Behavior and Bionomics 34(2):155-162.
    Pezalla, V. M.  1979.  Behavioral ecology of the dragonfly Libellula pulchella Drury (Odonata: Anisoptera).  American Midland Naturalist 102(1):1-22.

Acknowledgments
    My thanks to dragonfly experts Dennis Poulson and K.D.B. Dijkstra for help with the species identification and discussions about dragonfly postures.