I’m a fan of impressionistic art. Even though I don’t understand a lot of it, I still like to look at it.
If I was inclined to take up oil painting, I would definitely lean toward Impressionism because I wouldn’t be expected to reproduce someone’s face on canvas that equaled photographic accuracy and quality.
I could just suggest a person’s face and no one would complain. I wouldn’t have to duplicate a tree by painting each individual leaf or limb.
I would just need to suggest a tree and the art world would let me get by with it.
I have found it to be the same with fly tying. I like to consider myself an impressionistic fly tyer. That is… I don’t try to copy every little detail of the actual insect.
All I need to do is to copy the most significant or obvious detail or details of the insect. Size, shape and color are three of the most important characteristics to consider but sometimes there might be one or two other standout features of an insect that need consideration.
Whatever feature of the insect that is prominent is what needs to be matched at the tying table.
If the segmentation of the abdomen is the most noticeable feature of the insect, then by all means it should be emphasized on the fly.

If a certain caddisfly or mayfly is wearing a red Cardinal baseball cap, then my fly will have a touch of red yarn or dubbing tied in at the head of the fly. An actual cap is not needed… just a hint of something red.
All you need to do is suggest an insect and the art critic, in this case the trout, will allow you to get by with it. Precise duplication of a living insect is not needed to catch trout.