Insects?

How high do various critters go? Gnats? Mosquitoes? Ticks? Wasps? Bees?

At least 300+ feet, as the bees frequent the huckleberry bushes that grow in the crowns of the Coast Redwoods. A great book to read is "The Wild Trees" by Richard Preston. Red voles, ground salamanders, and even copepods (plankton) have been found in the fern beds and hollows of those magnificent trees.