Booklice
Also known as Psocids, Psocoptera, Liposcelis bostrychophila
In short
Booklice are tiny, pale, wingless insects that feed on moulds and starchy materials in humid rooms. They are sometimes found around damp potted plants on windowsills but do not feed on plants; they are a sign of high humidity and mould.
How it looks
About 1–2 mm (roughly 1/25 inch) long, soft-bodied and yellowish to buff; household species are wingless. They run quickly but do not jump. Found on damp surfaces, in cupboards, on books, and on mouldy organic matter.
Signs
No plant damage. Tiny pale insects running over damp window frames, saucers, pots, papers or stored food. Their presence points to mould growth nearby.
Life cycle
Egg to adult takes about a month, and adults live around three more months.
What favours it
Warm, humid rooms: they do best at about 24–28 °C and 75–90% relative humidity, and die within weeks when humidity stays at 50–60% or below.
Prevention
- Avoid overwatering and standing water in saucers on windowsills.
- Improve ventilation and reduce humidity with a fan or dehumidifier.
- Remove mouldy debris, food and papers.
Treatment
Start with the first step and move down only if the problem persists.
- Lower indoor relative humidity below about 50%; this also stops the mould they eat.
- Clean and dry infested areas and discard mouldy items.
- Insecticides are usually unnecessary.
Pros and cons
Pros
- Do not feed on plants.
- Feed on moulds, so they are an early warning of damp.
Cons
- Can contaminate stored flour, grain and cereals and damage damp books and paper.
- Indicate a mould or damp problem.
Look-alikes
- Springtails
- Springtails jump with a tail-like spring; booklice run.
- Mealybugs
- Mealybugs are covered in white wax, move slowly and sit on stems and leaves feeding on sap.
- Thrips
- Slender insects on leaves and flowers that cause silvery scarring.
Related
Sources
Written in our own words from these sources. Check a product label before using any treatment.