I had a beautiful blooming clematis this July. I was away for a week and came back to no flowers at all and the leaves were been eaten be something. No sign of snails or other insects on the plant at all. I could not see what was eating it. The leaves on the plant at the bottom were a yellowish colour but the top still green. I have seen greenish coloured house flys around it and they do land on it. Could they be eating my plant and if so how do I get rid of them?