A. I don't think anybody can answer this question, but I can make a couple of observations. On an individual basis, a midge larva probably contains more potential food energy than the adult. Thus, a trout would need less of them to obtain a given level of food energy. You might also expect that a trout would probably expend less energy picking up a midge larva from the drift or from a stone rather than taking it from the surface as an adult. Generally, trout take whatever is most available and easiest to get.