Mating "March" Flies. Notice the sexual dimorphism. Until I found them mating, I assumed these insects were two different species. The male has the bigger eyes.
Mating Dance Flies. Male is holding the threesome by two legs. The male delivers prey (in this case a fly of a different species - a Male March Fly) to the female, apparently to keep her distracted. I found about a dozen threesomes similarly engaged on a single small tree.