Sunday, May 6, 2012

Forktail Interaction

Western Forktails differ from many other damselflies in an interesting way.

If you go to a nice pond in the summer in Washington state, you are quite likely to see female Western Forktails.  They are pruinose blue overall, and quite easy to spot as they move along the shore laying eggs in one location and then another.  You don't see male Western Forktails, however.  It can be quite tough to spot a male.  What's going on?

Apparently, most female Western Forktails mate just once in their lives; after that they fend off other males who attempt to mate with them. A good example is shown in the slow-motion video below.  The video starts with a female Western Forktail minding her own business.  Suddenly a male races in to grab her and attempt to mate – not really much in the way or courtship, I'd say.  The female resists, and eventually the male moves on.  After getting this kind of treatment from the females, the males apparently move off into the bushes to forage and thus are not encountered very often.

According to Dennis Paulson in Dragonflies and Damselflies of the West, female Western Forktails are "very effective at repelling attention of male forktails and bluets by fluttering wings and curling abdomen tip down."  Here's a good example of that.

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