I just remember when I bought my dragon wings Ernie indicated dirty or blades with lots of smashed bugs will greatly affect the lifting performance of the blades. He indicated keep them clean and polished for the best performance.
Yep. One summer afternoon I flew off to a grass airstrip and did about a half-hour of touch & gos and skimming over pastures and on the way back I noticed that I was flying almost 10 mph slower than usual at my normal cruise power setting. When I landed I noticed that my blades were plastered with dead bugs. I cleaned them off and did a few more laps and my airspeed was back to normal.
A friend of mine had bought a Hughes 300 and had commented that lately it was taking more power than normal to hover. I pointed out the bug encrusted blades and told him that it would fly better if he cleaned them off. He scoffed at the idea but admitted later that after he had scrubbed the bugs off it was flying like normal again!