50 flies with one swat. Swarms of flies in every video. Drowning flies in the Race Point Gatorade. General complaints and exasperation from runners, volunteers, and spectators from downtown to the top. Bugs are to be expected, but the explosion in a particular fly, the March Fly, caused most of these issues.
Fortunately, the March Fly does not bite. Instead, the short-lived adults do not eat, or may feed on nectar and pollen. The slow-flying insects, about a 1/2″ long, are most abundant in wooded areas and moist sites. That would explain their presence in the trees going up the race trail, but not the swarms at the Race Point. Spectators?
Flies in general are attracted to white and bright colors. Providence Medical Care Center recently had to install high-powered fans to blow them away from the white CT scanner entrance. Race volunteers, sporting neon t-shirts and safety vests also attracted a collection of March flies.
Found throughout North America, swarms crossing highways have been known to reduce visibility and cause vehicles to overheat when the masses of dead flies clog unscreened radiators. The fatty tissue of the splattered bodies may pit or mar vehicle paint if not washed off. The North Carolina State University website offered this helpful advice: smear the front of the car with baby oil or no-stick cooking oil to aid in the removal of splattered flies later. <https://www.ces.ncsu.edu/depts/ent/notes/O&T/flowers/note35/note35.html>
Maybe next year, those speedy racers will also be smeared with baby oil to make it easier to wash off all the splattered bugs at the finish line!
PS I think they’ve been here, but they are not noticed until their population explodes. 2015 was another year with large numbers.
Ellyn: the caterpillars that decimated the alders, birch, willows, blueberries, raspberries, ornamentals, etc were a different insect, the larvae of the geometrid moth, aka Autumn moth, Bruce spanworm. Fortunately, their massive numbers subsided back to normal and most, but not all, plants have recovered. Large swaths of alders and willows died when too many of their leaves were eaten. There is more information on the web under “geometrid moth activity in southcentral AK” and other links.