Bugs, unlike beetles, have sucking rather than chewking mouthparts. Most bugs use their "beak" to suck up plant juices but some, like the "asassin bug", use it to suck juices from other insects. The size and number of segments in the beak are one among the key features that seperate the various families of bugs.

The vast majority of hemipterans, or true bugs, fall into the former category and are thus considered pests. Some are so damaging that they actually kill individual plants.