One of the things that flies have going for them that other orders of insects can’t match is the their sublime wing venation. Beetles hide their flying wings away under opaque wing-cases, butterflies and moths cover their wings with distracting scales, dragonflies wings are crazy paving complicated, caddis fly wings are drab, wasps too confusing …. you get the picture. But apart from the pesky Psychodidae (moth flies), flies present a single pair of unadorned transparent membranes, sometimes helpfully spotted in distinctive ways, but never in such a way as to obscure the quirky, family specific and aesthetically pleasing patterns of veins.
I particularly like the wings of Lonchopteridae which are symmetrical in outline, curving off gently to a pointed tip, the shape of a petal or a leaf, a wing designed to look good rather than for fancy flying tricks. The veins are relatively simple, each pursuing a steady course from a busy base to find its own patch of wing margin. There are no cross veins to confuse the picture, and just one forked vein to fill in a gap. Most endearingly, in females the vein nearest the hind margin of the wing joins up with its neighbour but in the males the vein keeps its distance and finds a solitary way to the wing margin.
Now, the most common difference between male and female flies, excluding their genitalia, is that males flies often have larger eyes that fill every bit of the top and front of their heads. Many of these male flies form mating swarms or otherwise chase down females, so the male goggle eyes make evolutionary sense. But what advantage can the subtle change in wing flexibility produced by having slightly different venation make? Perhaps whether or not those two veins meet is just an unintended and inconsequential consequence of some other more important difference between the sexes. Might it also be true that in our species men are prone, for no apparent benefit, to snoring, baldness, pot bellies and a tendency to take obsessive interest in particular aspects of their environment. I am only admitting to one of those.