Aster World, Part 11: Flower Flies

Next to bees, flies are the most important pollinators!  

There is a special category of flies called "Flower Flies," famiily Syrphidae. 

Many species of Flower Fly are bee-mimics.  

Flower Fly Dioprosopa clavata on
Symphyotrichum pilosum
Bird Runner Wildlife Refuge
McDowell Creek, Geary Co., KS
October 2021

But this fall a Flower Fly that is a wasp-mimic, Dioprosopa clavata, visited our volunteer Hairy Asters.

Such a tiny fly!    Such delicate markings!  

Look at that "wasp-waist":  

Look closely at the stems and you can
see why Symphyotrichum pilosum is
called "Hairy Aster."

                                                                           

The wasp-waist fooled me at first, and I thought this visitor was a tiny wasp.  But bugguide.net corrected my mistake.   I should have noticed the huge eyes.   They say "fly," not "bee" or "wasp."  

Flower Flies come in many sizes.   Eristalis stipator is about ten times the size of D. clavata and is a bee mimic.    In fact, I fell for the bee act when I first encountered this species years ago.   But this year I knew what it was! 

Here is E. stipator, resembling a honeybee and visiting our volunteer asters on October 15, 2021:

And here is Allograpta obliqua, mimicking a sweat bee and visiting our asters on October 11, 2021:

Sphaerophoria is another genus of Flower Fly that mimics sweat bees. 

Here is a male of that genus that visited our asters on October 16, 2021:

He too has large eyes, fly-eyes:

Here he is in action, feeding on the flowers and then grooming:

Syrphid flies are also known as "Hover Flies," as they can hover and zip back and forth, like hummingbirds.  

They are important pollinators and plant-protectors.  

The adults need the sugar in nectar to fuel their flights and the protein in pollen to produce eggs.   They travel from flower to flower gathering what they need and incidentally pollinating as they go.    

The females seek out plants that are vulnerable to aphid-infestation and lay their eggs there.   When the eggs hatch, the caterpillar-like larvae consume the aphids, protecting the plants.  In return, the plants provide nectar and pollen for the adults.  

The cycle continues!