Monday, September 25, 2017

Tiny Hover Fly

We were talking with friends when a few visitors buzzed us and finally landed, waiting patiently for their portraits.  I recognized them as a type of hover fly, aka syrphid or flower fly, but couldn't ID them initially.  BugGuide quickly identified them as Toxomerus politus.

Jacsun and his fly
Hover flies get their name from the way they hover in front of flowers while nectaring.  To the uninitiated, and presumably to predators, they look dangerous with colors suggesting a miniature yellowjacket.  These aposematic colors of yellow and black are common among some of the Syrphids but these are harmless flies that couldn't hurt a human.  
T. politus and their larvae (aka maggots) likely feed on corn pollen, and herein lies the puzzle.  We are a long way from a corn plant, likely 3+ miles and 300 feet altitude up to the Prairie View plateau.  Yet, here there are several of these flies looking fat and sassy.
Wikipedia mentions that "with a few exceptions, hoverflies are distinguished from other flies by a spurious vein, located parallel to the fourth longitudinal wing vein."  They show in the illustration on the left.  Out of curiosity, I zoomed in on one of our T. politus and sure enough, there it was.

Syrphid flies as a class are important contributors to our ecosystem.  Many species are pollinators and some species have larvae that are predatory, eating aphids in large numbers, potential agents of biological control.

Like the news bee which we recently wrote about, this and other hover flies seem to have an attraction to humans, visiting and sometimes even landing on us.  Try to appreciate them and hold your impulse to swat.
Way more information that we need on T. politus is available at this Syrphidae Community Website.