Q: This week I heard a sound coming from the woods that sounds like a fan running with a bearing that needs oil. It is loud enough that you can hear it from several hundred yards. Any ideas?

A: I’m pretty certain you’re hearing the rasping screech of periodical cicadas. They have been emerging for more than a week in middle Georgia. Few are seen in Atlanta because our landscapes have been so disrupted over the last hundred years that the periodical cicada population is minuscule. These cicadas live underground for 13 years then hatch en masse for a couple of weeks. After leaving their soil cells, they molt out of their translucent skin and climb trees to make mating calls by rubbing their wings. When thousands are calling at the same time, the noise is quite loud. They are harmless and will disappear in a week or so.