The Blue Quills are small mayflies (hook size 16-20) but they can hatch in incredible numbers at a time Blue Quill Spinners begin to appear within hours after a hatch.
Although the spinner fall can occur in the early mornings, it usually happens late in the afternoons just before dark. On very overcast or rainy days the hatch is usually more intense.
They may be mixed in with the Blue-winged olives. Since they are about the same size of some of the baetis species, the same fly may work for both, even though the Blue Quills are much darker in color