Bug FAQHouse Psocid
Liposcelis bostrychophila · Order: Psocodea · Family: Liposcelididae
Also called: Bark lice
Source: Wikipedia, Penn State Extension
The house psocid is a tiny, pale brown, wing-less insect about 1 mm long. It lives worldwide in grain stores, warehouses, factories and homes where dry foodstuffs are kept, especially in humid, dark areas.
Source: Wikipedia, Penn State Extension
How to recognize it
It is pale brown, wingless, and about 1 mm in length. It is most common in cereals and other stored grain products.
Source: Wikipedia
Size
Adults measure roughly 1 mm (0.04 in) long.
Source: Wikipedia
Is it a pest in the house?
It is a common pest of stored products worldwide. It is notable for its high reproductive rate and resistance to chemical control. It infests humid, damp indoor areas and feeds on mold, fungi, paper, books, wallpaper, flour and other stored grains.
Source: Wikipedia, Penn State Extension
Does it bite or sting?
Booklice do not bite.
Source: Penn State Extension
How to get rid of it
Chemical pesticides are problematic in food settings due to cost, residues, worker safety and resistance. The best control is to fix moisture problems; lowering humidity below 50 % prevents mold and booklouse growth.
Source: Wikipedia, Penn State Extension
Where it lives
Found worldwide in grain stores, warehouses, factories and households where dry foods are processed or stored. Indoors it prefers humid, damp, dark places.
Source: Wikipedia, Penn State Extension
What it eats
It feeds on cereals and other stored grain products. It can also damage stored eggs in mosquito-rearing facilities.
Source: Wikipedia
Life cycle
Females reproduce mainly by parthenogenesis and produce about 200 eggs each. Eggs hatch to nymphs that look like adults and undergo four molts, reaching maturity in about 40 days.
Source: Wikipedia
When you see it
Development can pause in diapause, allowing survival up to two months without food. Sexually reproducing strains with both sexes have been found in Hawaii and Arizona.
Source: Wikipedia
Where it comes from
It has a worldwide distribution.
Source: Wikipedia
Lookalikes
Because of their flattened shape they can be mistaken for bed bugs, but bed bugs are larger and rounder. They are also much smaller than common grain beetles such as rice weevil or maize weevil.
Source: Penn State Extension, Wikipedia
Where it is found in the US
Recorded in 4 of 51 states and DC. Most records: California, Illinois, Indiana, Alabama.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
How can I get rid of house psocids?
Fix moisture issues and keep humidity under 50 % to stop mold and booklouse development.
Source: Penn State Extension
Why are they found in my pantry?
They thrive in humid, dark areas where stored grains and other dry foods are kept.
Source: Wikipedia, Penn State Extension
Same family (Liposcelididae)
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Liposcelis_bostrychophila
- Penn State Extension: https://extension.psu.edu/booklice
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-24 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.