When they positioned the instrument within one centimeter of aphids and delivered a two-second stream of room-temperature air, no aphids abandoned the plant. Similarly, adding carbon dioxide or volatile chemicals common in breath had no impact on aphid behavior. It wasn't until the temperature and humidity of the airstream were increased that there were noticeable effects. Altering either parameter alone produced only modest increases in aphid dropping, but the combination of increased warmth (to 35 degrees Celsius) and humidity (at 90-100 percent) caused nearly 40 percent of the aphids to plummet. The results were published online August 9 in Current Biology.