Tuesday, March 31, 2020

Shall We Dance?

My title reminds me of Fred Astaire and Ginger Rogers.  For the younger generation, I suppose other movies come to mind, maybe with Richard Gere; but how many of you think of flies?  Yes, flies.  There are some marvelous dancing flies – especially midges and dance flies.  A few days ago Dale and I were watching dance flies.  The fun began on a sunny day.  I want to say ‘a warm sunny day’ but it wasn’t all that warm – about 60 degrees.  Spring flowers are just coming out; grass is growing; bumble bees and dance flies are on the wing. 

First let me introduce the characters in this little saga. 
This is a female dance fly (Family:  Emphididae.  Subfamily: Emidinae).  Her abdomen is very pointed and her eyes have a little space between them.  Many female flies have a space between their eyes whereas the male’s eyes often touch.  She is sipping nectar on an English daisy, an early spring flower which is about an inch across.  
And here is a male.  Note his eyes are close together and he has a lumpy rear.  Both are small, about as long as a good sized house fly.

Note:  Emphididae is a very diverse family, so what I observed does not necessarily apply to all ‘dance flies.’
I’m looking for insects visiting one of  Oregon’s early blossoming bushes, a red current.  A big queen bumble bee zips from one flower to another, there are several honey bees, a hairy flower fly visits momentarily...

I’m missing the real excitement!  Off to the side I see half a dozen small flies circling up and down in a patch of sunshine.  The sun hits the sturdy hog wire fence that surrounds the garden where I stand.  The flies could easily fly between the square openings; instead the fence seems to provide an invisible barrier.  The flies bounce up and down in front of the fence – dance flies!

Since the fence seems to be a barrier, I have a chance of getting a photo of one. 
I love the challenge of photographing birds and bugs ‘on the wing.’  These are difficult, but once I succeed in getting a reasonably sharp shot, I can see it’s a male carrying a nuptial gift, hoping for an interested female to come along.  I photographed the female, shown at the beginning of this blog, five years ago.  Afterwards I read about these dance flies and hoped someday I’d get to see more.  

Here I am, with a dance fly dancing in front of me!  He carries a fairly heavy load – circling up and down in the sunshine.  He even lands to rest for a few minutes before continuing on with his dance. 

Suddenly a second fly zooms in and the two briefly spiral together -- sorry, no photo of that!  This male and female zoom up into a tree above me.  Out of sight.

Soon I try to focus on a second male.  Midair he connects with a female in front of me!  The two land on the stem of a wood vine which grows on the hog wire fence.  They have far more on their minds than Dale’s and my cameras. 
I see how useful those long legs are.  The male actually hangs from the wood vine stem with his two front legs.  His second and third pair of legs reach down and around the female while he continues to hold onto his nuptial gift – a march fly (Bibio sp.).  While the two dance flies couple, the female dines on a march fly slurpee i.e. she inserts her proboscis into the fly and sucks its juices.  I can even see the protective sheath which covers her proboscis until it is time to feed. 

Here is a view of a second pair.  This male landed on the hog wire fence and faced in such a way that shows off his long front legs; his middle pair holds onto her head; and his third pair still holds onto his nuptial gift -- a rather small offering this time. 

Other members of this genus can be quite devious.  The male creates an obvious  ‘nuptial offering’  out of either silk or bubbly froth …. And this is where the devious part comes in.  Sometimes the ball contains a real offering for the female and sometimes it is empty!  The dance flies I was watching were good, stalwart fellows, offering their ladies a juicy insect in return for favors wanted.