Olives or Midges

A few Olives
A couple hundred Olives

In the winter you spot trout rising to feed on the surface. The insects are very small but you finally catch one so you can match it. You are not real good at entomology and you don’t know if its an olive mayfly or a midge but you know the angling tactics are different. Simple. If it has a tail its a mayfly, if not its a midge.