Wednesday, August 3, 2011

Odonata Sex

Sex is complicated among the Odonates.  First a male transfers sperm from his testes at the end of his tail (abdomen) to a structure under his body (thorax).  Then he grabs his mate by holding on to the back of her head with claws at the tip of his tail.  The female then reaches her abdomen up to the sperm storage organ under the male's body.  Once connected, the dragonflies are said to be in the Wheel Position.  The pair of White-faced Meadowhawks in the photo above are in this Wheel Position.

Copulation, which can occur in flight or when perched, commences with the male flushing other males' sperm out of the female.  Next he deposits his own sperm.  Fertilization can last an hour or more. Next the female needs to lay her eggs in the water.  Often the male guards against other males' mating with her. As in the photos of the two Stream Bluets below, he flies attached to her until her eggs are laid. Otherwise another male may come along, flush the first male's sperm out, and replace it with his own.

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