The booklice (Psocoptera), also called barklice or barkflies, are an order in the class insects (Insecta), the subclass winged insects (Pterygota) and the infraclass Neoptera. Psocoptera comprise approximately 2, 700 species, and are found throughout the world. In Central Europe around 100 booklice species occur.
Booklice reach body lengths of 0. 5 - 10 mm. Most species have brightly coloured bodies. Their antennae are long and thin. Their mouthparts consist of an intermediate form of tools to chew and suck. Some species also have spinning glands. The males forewings at their rear edge are reversed like a hook and thus hand along the thicker front edge of the rear wing, while the females have stunted forewings or no forewings at all.
Based on the shape of their segments (antenna limbs) and foot joints, booklice are divided into 3 suborders, namely Trogiomorpha, Troctomorpha and Psocomorpha. Most species found in Germany belong to the Psocomorpha.
The booklice live on different plants, tree trunks, under tree bark, in dead wood, bird nests and even in buildings. They eat fungi, spores, algae and lichens. Occasionally they also eat dead insects. Booklice need a medium to high humidity and temperatures over 15 degrees Celsius and are capable of absorbing water vapour directly from the air. New buildings and buildings with mould infestations are a favourite habitat of booklice. Here the booklice increase the spread of the mould. They can also cause allergies, although this is mainly due to their excretory products.
The pseudoscorpion Chelifer cancroides, which also resides in human environments is a natural enemy of the booklouse. Psocoptera have a life expectancy of up to 12 weeks. A female booklouse is capable of laying up to 120 eggs. Thus, in favourable conditions (in buildings) booklice can produce 8 new generations in a lifetime.
