German cockroaches are the perfect pests—they’re small, they reproduce rapidly, and they have few natural indoor predators. Additionally, their stomachs have adapted to be able to survive on a huge variety of food sources, and they’ve developed resistance to many common pesticides. The combination of all of these factors means a few adult cockroaches that find a home in a human dwelling can turn into a large, difficult-to-kill infestation in a short period.