Sunday, May 27, 2012

Odonate Additions

On Friday at the University of Minnesota Landscape Arboretum, Erika and I found two unfamiliar dragonflies. Oddly, I already had photographs of both, except that previous photos were all of females. This season's odonates are males. The top critter is a Horned Clubtail, a species I first found in the Carleton Arboretum and blogged about on 20 September 2011. I needed assistance identifying the clubtail because this species' tail is not clubbed, but rather has widely branched cerci, the spines at the end of the abdomen. Thanks, as always, to Scott King for his help.
The second photo is of a Dot-tailed Whiteface. I found this species in Dakota County and made a post on 6 October 2011. On Friday, a male flew up from a duckweek-filled pond and, in midair, attached himself to a female. In a fraction of a second, the pair assumed a "Wheel Position." The two Whitefaces, now in tandem, landed back on the pond.

Kurt Meade (Dragonflies of the North Woods) writes, "mating is usually initiated by the male who, with the grace of a professional wrestler," curves his abdomen forward, and attaches the end to the back of the female's head. This behavior is to assure no other males visit his mate. The female then obtains sperm by attaching the end of her abdomen to his sexual organ. Sperm transfer is accomplished only after he purges other males' sperm from her genital opening. Meade concludes, "the time needed to complete fertilization ranges from 15 seconds to well over an hour."

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