We go turkey hunting in southern Ohio usually the first weekend in May. Three years ago we started seeing fireflies (lightning bugs as we call them here) there in the evening. If you haven't been in southern Ohio cleaning then there must be a larger answer. Maybe I should contact the head entimologist at our local college.

Tonight, about 9:20 pm (4/12/10), I saw several fireflies high in the trees around my home in east Tennessee (in the Smokies' foothills). None flew lower than 30 feet up; they were mostly blinking at 50-70 feet, high in the canopy of the forest.

I could find no reference to April fireflies, or to fireflies flying so high, in either of my insect books.