Have you ever fished when you know the trout are eating, but you can't tell what's on the menu? I'm not talking about having trouble with insect identification, I'm talking about when you can't even see the bugs that the fish are eating! Micro midge activity, can be a tough day on the water if you don't have the right fly (see the 2nd photo below). On the other hand with the right fly it can be the most productive day of fishing you have ever had. Anglers typically do not like to use these small flies (which is another reason why they work so well), but from experience they are worth the extra effort of tying them on and using light tippet. Most days when the trout key in on these ultra small midge larva or pupa you do not have to tie on another fly all day (unless of course you break off).
#30 midge larva. Don't be afraid of this hook. It is not that hard to tie, you can fit high quality 7X tippet through the eye, and they actually hold on to fish!
The 'big' fly in focus is a #20 midge larva. This picture shows the true size of these micro midge flies.
#26 midge emerger with krystal flash wings. Many times #26 is as small as you need to go. With a little practice this size fly can produce a high land:loose fish ratio.