Willi & Sue wrote in
:

BWO's (at least out West) aren't a "family" in the scientific
sense. There are many different insects that are referred to as
Blue Winged Olives. They vary in size (usually small), color and
other characteristics. Many BWO's aren't blue or olive. To my
eyes, most are varied shades of gray.

snipped interesting stuff

Good info Willi. Local rivers here in the Northeast do exhibit the
same variety in size for Olives, but they do all have blue to slate
colored wings and are all olive, at least on the bottom of the
abdomen (trico duns also have olive bodies making the BWO a good
choice early in the hatch before the fish focus on the spinner fall).

There are large olives in the Spring and smaller varieties as the
season progress. The waters I fish don't see the pods of feeders you
refer to, but when there is a decent hatch going it will usually be
the choice pattern over all else on the water. Cloudy days in Vermont
about this time of year are wonderful for both olive and caddis
hatches and one of my favorite times to fish. The scenery is not too
shabby either!