There are few things that can put the missing piece to the puzzle like taking a throat sample. When done properly it does not harm the fish, and you can get an exact reading on what the fish are choosing to eat on that given day. Throat sampling is essentially drawing up what the fish has recently eaten, and you can expect most of the bugs to still be alive.
Super, super nerdy. I mean, I really try to tell as few people as possible that I like to force fish to regurgitate the bugs they ate for lunch, so that I can put them in a glass vial and take photos of them with a macro lens. However, this does allow you to get a perfect idea of what can be created at the tying bench.
Now for the main event, what do different coloured chironomid pupa in the throat sample mean for the angler? The body colour on the pupa can reveal a lot about where fish might be feeding in the water column. If you are seeing chironomid pupa that have residual hemoglobin towards the back of their body, or very dark and earthy shades such as black, brown, olive and maroon, then fish are likely feeding close to bottom.
On the flip side, if you are seeing that the fish are stuffed with shiny, bright pupa that have almost a platinum tone to them, then you are most likely dealing with fish that are suspended in the water column. These shiny bugs mean that they were intercepted a little ways up their ascent, it is not uncommon to find fish feeding 10 feet off of the bottom at times.