The term 'Cupboard Invaders' refers to ants, which are four-letter insects that are known for their ability to invade cupboards and other areas of the home. Ants are small, social creatures that live in colonies and can be found in many different habitats around the world. They are often considered pests due to their ability to cause damage to food sources and other items in the home. Ants can also spread disease and contaminate food, making them a nuisance to homeowners.