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Dragonflies and Damselflies -- Odonata

The Odonata come in two flavors: dragonflies or Anisoptera and damselflies or Zygoptera. Dragonflies have their wings spread when perched as in the picture above of Celithemis elisa. Damselflies perch with their wings together or slightly spread as in the picture of Ischnura posita below. Damselflies also have identical front and hind wings, while those of dragonflies differ front to back.

The first thing you will notice about Odonata is their eyes. They occupy nearly the entire head in dragonflies and you will note that the animal is always turning its head this way and that. They have superb vision, but we haven't a clue what they actually see (what image if any appears in their mind).

This time of year you will probably mostly see little brownish or reddish dragonflies -- even on the Brown Green. These are an odd species that lays its eggs where there is no water -- yet. The eggs will wait until the spring rains to hatch. Most other odonates lay their eggs in water or put them inside plants in or near the water.

What got me interested in odonates is their odd way of mating. The male first grasps the female behind the head with a pair of appendages on his abdomen. This results in what is known as a tandem or tandem pair. The male must then transfer sperm from his abdomen (near where he holds the female) to a special copulatory organ at the base of his abdomen. After that, the female must bend her abdomen forward to engage her genitalia with his, resulting in a copulatory wheel. Actually most of my colleagues refer to it as a "heart: not a "wheel". It is during the copulation that follows that the male removes or pushes aside most or all of the sperm she has stored from matings with previous males. He then replaces it with his own.

The pair remain together in tandem while she lays her eggs or they seperate and the male remains nearby chasing other males away.

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