I cut a couple of medium sized Black Walnut trees that were growing on the edge of a small prairie patch beside the house. The trunks were about four inches in diameter, so after stripping off the branches, I left them in the lawn beside the barn to cut up for firewood. When I returned from adding the branches to the brush pile, I found the logs being used as a perch and hunting platform by a swarm of small Robber Flies.
Robber Flies come in all sizes, but it’s usually the large species that get all of the notice. Being extremely tiny doesn’t keep these guys from being quite attractive and interesting. Sunlight on the transparent wings produced a shifting pattern of pastel purple, blue and green.
These are predators that feed on other small insects. Each log had dozens of flies taking advantage of the slight elevation above the lawn grasses to watch for passing prey items. When you’re that small it doesn’t take much of a rise to put you well above the action.
Prey of the day appeared to be small leaf hoppers. The hoppers were so small that I couldn’t even see them in the air. The Robber Flies with their super sized eyes had no such trouble. Each quick trip out from the log resulted in another capture.
A variety of leaf hopper species were being captured. Unfortunately, I couldn’t identify them with any more accuracy than I could the Robber Flies.
I watched the Robber Fly action for quite a while. The flies would eat the select portion of the leaf hoppers and then drop the remains before heading out for another capture. I didn’t want to disturb the action, so I left the logs where they lay. I’ll finish cutting them up some other day.