Obelisk posture
The Obelisk is a handstand position similar position ( Odonata ) are taking some dragonflies to prevent overheating on sunny days. The abdomen (abdomen) is then aligned directly at the sun, and so minimizes the body surface of the heat radiation exposed. When the sun is at its zenith, reminds the vertical alignment of the dragonfly on an obelisk.
Occurrence and function
The obelisk position was over 30 species of the families of the Demoiselles ( Calopterygidae ) Virgin River ( Gomphidae ) and especially the sail Dragonflies ( Libellulidae ) were observed. All are predators that lurk from their residence dating back to loot. The achieved by the obelisk position thermoregulation enables them longer despite the heat on the positions to remain.
Under laboratory conditions, by the shine on with a 250 watt lamp, the obelisk position can also be caused experimentally. Pachydiplax longipennis lifts the abdomen at high temperatures and reduces it in the shade correspondingly again. It was shown that the behavior is an effective measure to prevent or slow down the body temperature increase.
Dragonflies can raise their abdomen for other reasons. Males of the type mentioned above take the obelisk position one also, if they guard their territory and to present to the best advantage for impressing other males the blue wax tires of the abdomen.
Other forms of physical thermoregulation
Some dragonflies, for example Hagenius brevistylus reduce the heat radiation by aligning her abdomen downward, away from the Sun. The tropical sailing dragonfly Diastatops intensa whose wings are mostly black, shows with the wings instead of the abdomen to the sun, apparently to them of radiation that they absorb less to complain about.
Some members of the genus Tramea lower their abdomen during flight in the shadow region, which is caused by dark areas on the wing base of the hind wings. The same behavior shows Pseudothemis zonata with similar Flügelmahl.
The position of the sun can be utilized to increase the body temperature. Keeping seated in the thoracic flight muscles hot is particularly important for dragonflies because they could not fly otherwise. Some can move their wings so that they reflect solar radiation to your body or form with the wings a kind of greenhouse over the thorax, which absorbs the heat of the substrate. When the sun is low, set dragonflies their abdomen perpendicular to the radiation, in order to maximize the surface area exposed to direct sunlight. Similar to this behavior, the obelisk position, but it fulfills the opposite purpose.