Obelisk (biology)

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Obelisk (biology)

The term obelisk in biology refers to a specific posture adopted by certain species of dragonflies and damselflies to regulate their body temperature. This behavior is particularly observed in the family Libellulidae, which includes many common dragonflies.

Description

The obelisk posture involves the dragonfly raising its abdomen vertically, pointing it towards the sun. This position minimizes the surface area exposed to direct sunlight, thereby reducing the amount of heat absorbed. The term "obelisk" is derived from the resemblance of the dragonfly's raised abdomen to an obelisk, a tall, four-sided, narrow tapering monument which ends in a pyramid-like shape at the top.

Function

The primary function of the obelisk posture is thermoregulation. Dragonflies are ectothermic organisms, meaning they rely on external sources of heat to regulate their body temperature. By adopting the obelisk posture, dragonflies can avoid overheating during the hottest parts of the day. This behavior is crucial for maintaining optimal body temperature, which is necessary for efficient metabolism, flight, and other physiological processes.

Species

Several species of dragonflies exhibit the obelisk posture, including:

• Common Whitetail (Plathemis lydia)
• Eastern Pondhawk (Erythemis simplicicollis)
• Blue Dasher (Pachydiplax longipennis)

Related Behaviors

Other thermoregulatory behaviors observed in dragonflies include:

• Basking: Spreading their wings to absorb heat from the sun.
• Shade-seeking: Moving to shaded areas to avoid excessive heat.
• Perching: Resting on vegetation or other surfaces to regulate body temperature.

Related Pages

• Dragonfly
• Damselfly
• Thermoregulation
• Ectotherm
• Libellulidae

See Also

• Behavioral thermoregulation
• Insect behavior