These insects are not related to the true lice. They prefer damp places, such as cellars, damp outside walls, or outhouses, and they may be found in new houses before the walls are dry. They cannot tolerate dryness.
A female booklouse can lay a couple of hundred eggs, and under favourable conditions development to sexual maturity takes about a month, so it is not surprising that booklice often occur in very large numbers. In kitchens and stores they mainly attack flour, cereals and other goods containing starch, and they have a fantastic ability to get into packets that are not tightly sealed. They are in no way dangerous to health, but may cause commercial losses if they become established in grocery stores.