Tuesday, May 15, 2012

Spiny Baskettail Dragonfly

Spiny Baskettail - Tetragoneuria spinigera
These dragonflies emerge en masse every spring at Westwood Hills Nature Center.  Usually their emergence is at the end of May, but this year they were about two weeks early.
There are three species of Baskettail dragonflies found in Minnesota: Spiny, Common, and Beavertail.  They are best identified by looking at the shape and size of the paired appendages (called the cerci) found at the end of the abdomen.  The cerci (along with the epiproct, located below the cerci) is used by male dragonflies to grasp the female during copulation, and helps direct the females genitalia to the males hamulus, or secondary genitalia, where the sperm has been transferred to.  Mating in dragonflies is a pretty complicated affair in dragonflies, and often highly competitive.  For more details, refer to "Dragonflies of the North Woods" by Kurt Mead, which has a short and clear description of the process.  I also highly recommend sitting on a dock and just watching dragonflies for awhile.