Hi and thanks for your great pictures of the fourth stage of a Brown Marmorated Stink Bug... not an adult, yet but very bad news. They are an invasive species and suck the juices out of so many crops, from raspberries to apples, grapes and pretty much anything juicy. You can see the long "stylet" on the underside in the third picture. It reaches nearly as long as the body and is what is inserted to suck the juice out.

So crush away with a clear conscience as not much else eats them and they do lots of damage.