Cicadas only live for a few weeks, mate, then die. However, when millions of the insects come out at the same time things get a little crazy. At its peak, their mating call hum was like your neighbors all cuting their lawns at the same time, all day long. Then as quickly as it started, the hum it stopped.
After the cicadas mate, the female scrapes a channel in small twigs or branches (anything up to the diameter of a pen) and deposits her eggs. Here's an example, with the scrapes circled in red.
Thanks to Saralynn at Yeah, but Houdini didn't have these hips., now I know. If too many female cicadas use the same branch, the twig gets weak and fall to the ground. The process is called flagging, and just like the cicadas, flagging is temporary and will be over soon.