Illinois Natural History Survey - University of Illinois

Observing Dragonflies

 

Carolyn Nixon

 

Dragonflies are active throughout the daylight hours and are often colorful and easy to observe.  When you visit a wetland, pond, or stream, see how many of the following dragonfly behaviors you can observe. Before you begin, write your name, the date, time, and weather conditions (temperature, windy or calm, cloudy or sunny) on your paper.  You can create a list of the behaviors and make a check mark for each time that you observe the behavior.


 

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Emergence—a dragonfly or damselfly nymph will leave the water and climb up a plant or rock.  Its skin will split along the dorsal (back) side of the thorax, and the adult dragonfly will pull itself free.  It will then sit as its wings expand and its exoskeleton hardens.

 

cast_skin.jpgCast skin—the dragonfly will leave the empty skin of the nymph behind.  These can be seen clinging to rocks and plants.

 

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Courtship—the male dragonfly will cling to the back of the head of the female, using claspers on the end of his abdomen.

 

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Mating (wheel position)—the male will attach the end of his abdomen behind the head of the female, and the female will attach the end of her abdomen to the base of the male’s thorax.

 

Oviposition (egg laying)—dragonflies lay their eggs in a variety of ways.  Some stand at the edge of the water and dip their tail into the mud; others fly over the water, either just the female, or male and female attached together, and the female will dip her tail into the water.  Still others will cling to a plant stem in the water and back down it, lowering the end of their abdomens into the water along the stem.

 

Patrolling—dragonflies cruise their territory, often zig-zagging back and forth as they look for prey. When they detect insect prey, they will veer upwards or sideways suddenly as they pursue and capture their targets.

 

Gleaning prey—they may also hover over vegetation looking for prey on the leaves.  If they spot something, they drop quickly to the plant. 

 

feeding_damsel.jpgConsuming prey—if a dragonfly captures a tiny prey item, it may eat it instantly.  For larger prey, it may return to a perch to consume it, usually removing the wings and eating it head-first.

 

Grooming—dragonflies must remain perfectly clean and can sometimes be seen grooming by moving their legs across their body, eyes, or wings.

 

ThermoregulatingBlueDasher.jpgThermoregulating—dragonflies are able to raise or lower their body temperature to some extent.  To lower body temperature on a hot day, a dragonfly will point the end of its abdomen up into the air (obelisk position) or it my hold its wings forward and slightly downward.  To warm its body on a cool day, it may vibrate its wings while perched.  

 

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Perching—dragonflies often sit atop plant stems or on a leaves.  They may be basking in the sun or surveying their territory.

 

If you see other behaviors that do not seem to fit in one of the categories, describe it on your sheet.

 

Damselflies, smaller and more dainty relatives of dragonflies, also practice the same behaviors, but are more difficult to observe.  You can record the same information for damselflies, as well.  If you do record behaviors for both dragonflies and damselflies, be sure to note which you observed.  You might want to use separate columns for each group.

 

 


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