These large, cryptic stink bugs have been hanging around the trees by my house lately, often clustered up against the bark and nearly undetectable by casual observation. Like other hemipterans, stink bugs (or pentatomids) have sucking mouthparts, which they use to feed on plant matter. We also have a fairly common bright green stink bug that does a good job blending in with leaves and stems.
Stink bugs get their common name from the strong deterrent odor they emit when disturbed. This smell, combined with an unpleasant taste, helps to ward of predators. This is not unique to stink bugs, however: several other hemipteran families also have scent glands. Unlike such smelly animals as the skunk, I find the smell of stink bugs not particularly unpleasant–a bit like sickly sweet fruit. A casual survey of various people I have had the opportunity to quiz on the subject (“Here: smell this bug!”) supports my opinion.
The stink bug family name Pentatomidae means “five divisions” which may refer to the five-segmented antennae (many other hemipterans have only four) or the somewhat pentagonal body shape.