NC State Extension Publications

Description and Biology

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Common barklice, Cerastipsocus venosus, are small, fragile, sometimes strikingly marked insects that have chewing mouthparts and relatively large heads. Adults have long antennae and four wings that are held roof-like over the body. They grow to only 1/8 inch long, but are conspicuous when they band together in "herds" on the trunks of trees and shrubs (Sometimes they are referred to as bark cattle.). Females lay eggs singly or in clusters and sometimes cover the eggs with silk or debris. Nymphs hatching from eggs resemble tiny wingless adults. Most species develop through six stages. Nymphs are dark gray with pale bands between abdominal segments. Nymphs are also gregarious and cluster together on the bark. Nymphs appear in April. All stages are harmless to the shrubs and trees they live on. Bark lice sometimes live under layers of silken webbing. Barklice feed on molds, fungi, pollen, fragments of dead insects and other detritus. None of the barklice are capable of injuring plants and therefore the term "louse" is misleading.

Cerastipsocus venosus on a crape myrtle branch

Common barklice are most frequently observed on smooth-barked trees.

A group of common barklouse nymphs on a crape myrtle stem

Common barklice nymphs "herd" together on the bark of trees and shrubs.

J. R. Baker

Host Plants

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Common barklice are found on the trunks and stems of various trees and shrubs where they do no harm other than alarm amatuer horticulturists. They are most often noticed on smooth-barked shrubs and trees such as crape myrtle, sycamore, and young oaks.

Residential Recommendation

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Since barklice do not harm plants, no pesticide recommendation is needed. However, if control is desired, spray infested stems with water to dislodge and drown them. Any contact insecticide should give more than adequate control.


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For assistance with a specific problem, contact your local N.C. Cooperative Extension Center.

This Factsheet has not been peer reviewed.


Professor Emeritus
Entomology and Plant Pathology

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Publication date: Dec. 13, 2013
Revised: Nov. 3, 2023

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