Bug FAQYellow barklouse
Valenzuela flavidus · Order: Psocodea · Family: Caeciliusidae
The yellow barklouse is a small, yellow-black insect that lives on a wide range of trees and shrubs. It feeds on microscopic organisms that grow on the bark and leaves of many plant species, including alder, ash, birch and oak. It is found in the United Kingdom, sometimes Ireland, and is also widespread in the Near East.
Source: Wikipedia
How to recognize it
The insect is yellowish-black in colour.
Source: Wikipedia
Where it lives
It likes to feed on plants such as guelder rose, rhododendron and rowan berries.
Source: Wikipedia
What it eats
It eats microflora on many trees, including alder, ash, birch, oak and pine.
Source: Wikipedia
Where it comes from
It occurs in the United Kingdom and occasionally Ireland. It is also widespread in the Near East.
Source: Wikipedia
Lookalikes
It was originally named Psocus flavidus by Stephens in 1836.
Source: Wikipedia
Where it is found in the US
Recorded in 37 of 51 states and DC. Most records: Tennessee, Virginia, Missouri, Massachusetts, North Carolina, Michigan, New York, Georgia.
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
What does the yellow barklouse look like?
It is a small insect with a yellow-black colour.
Source: Wikipedia
Where can I find yellow barklouse?
It lives on a variety of trees and shrubs in the UK, Ireland and the Near East.
Source: Wikipedia
What does the yellow barklouse eat?
It feeds on microscopic organisms that grow on the bark and leaves of many tree species.
Source: Wikipedia
Same family (Caeciliusidae)
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Valenzuela_flavidus
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-22 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.