Bug of the Week: Bark Lice or Tree Cattle

What would you do if you saw a cluster of these insects on your tree?

They do look a bit odd, like creatures from a Dr. Seuss book with yellow and black striped pajamas .

No worries, though. They are bark lice nymphs, Cerastipsocus venosus (family Psocidae) and they are actually quite cool. 

The nymphs have plump abdomens, rounded heads and long antennae. The adults look similar, but have wings which fold over their backs. BugGuide has photographs of the adults.

Bark lice are found on the bark of trees, but the name is unfortunate because they aren’t really like the parasitic lice that animals get.

Instead bark lice feed on lichens, debris, etc. found on the outside of trees. A better name would be “bark groomers”.

They also go by the common name “tree cattle” because they group together in tiny “herds”. When disturbed, they run together, looking like a herd of cattle stampeding.

This video shows their swirling movement while trying to escape a potential predator (stick).

Doesn’t it look like a flock of migrating birds moving together in the air, turning this way and that?

 We found these tree cattle in western New York State, but you might see them throughout North America’s Eastern Deciduous Forest.

So, now that you know what they are and a little bit about them, what would you do if you saw these benign insects?


  1. James C Trager

    Bark groomers – I like it!

  2. Roberta

    We could always start a movement to change the name.

  3. Nancy

    I have them not scared just was afraid of hurting my tree what was the stick bug the mother because it had eggs on it

  4. Max

    Thanks for posting this! I saw these guys for the first time at Bon Echo, Ontario, while camping. I saw my first little herd while tieing a tarp rope to a tree. At first, I noticed how they looked kinda funny like little metal springs, then I gently disturbed them and found out they moved together as a group! I definitely thought of them as a herd of cows lol, and by the looks of them, I had a feeling these were good bugs.

    Thanks for sharing all the extra info. Knowing they groom bark makes me like them all the more! Tree Cattle, Bark Groomers, love the names 😀

    Wow, just looked at their adult form. They look quite serious when they have their wings!

  5. Roberta

    Glad you took the time to share your experience. Awesome!

  6. Kenna

    I’m seeing these by the thousands in Harrison County Indiana. Thanks so much for the info!

  7. Roberta

    Of course! Thank you for letting me know.

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