There's a lot of variation between species, and even between scales on the same wing, but I find the spacing between "rungs" is often at the resolving limit of a 0.55NA objective. Some are spaced more widely though. So I was hunting for scales with wide-ish spacing to test APS-C mode on my camera and see what it did for the performance of my 50x mitty on a 135mm tube lens (while avoiding those unsightly lower quality image edges that appear in full-frame mode).
I came across this example - an unknown species from a box of random wings. The image covers a 0.7mm wide FoV (APS-C sensor area, no crop in post), a stack of 50 images. There seems to be a correlation between scale colour and rung spacing (darker colour=closer spacing). Not saying that's a universal thing - just a passing curiosity...
