What is this insect
This is a yellow jacket. Yellow jackets are a type of wasp and live in colonies, like honey bees do.
Yes, normally they nest is in the ground, but that's because they nest in voids--and sometimes they find a void in an unusual place. In the ground, we normally would recommend spraying with a hornet and wasp spray. You might want to try using one of the granular formulas. Figure out exactly where the entry is first. Be sure they are calmed down for the night before applying pesticide. Cool weather is better. Either evening or early morning, as long as there is enough light to see what you're doing.
At any rate, you'll end up with dead insects in your furniture. The fewer the better, so don't wait for the population to get huge before you tackle this. Do it as soon as possible.
Here is our website info on wasps: http://extension.umd.edu/learn/summer-stingers-%E2%80%93-eastern-yellowjackets-vespula-maculifrons