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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?

So, what do you bring with you to pick blueberries?

Of course you need your hat and buckets.

But you also might want your camera.


You might need to take a few photographs of the blueberries to remember the day.

You also might want to take a photograph of some newly-hatched shield bug nymphs.


Take a close look at the one on the bottom. It still has the circular lid of its egg stuck to it.

The nymphs look like they are too big to fit in those egg shells, don't they?

What insects have you found in a blueberry patch?


Thank you to Justin for holding the leaf upside down so I could take the photograph.


We have shown photographs of assassin bugs before, but let's learn more about them.

(Assassin Bug Egg Mass by Jim Kalisch, UNL Entomology)

Assassin bugs start out as eggs like the ones above.

The eggs hatch into colorful nymphs. They are small at first.

Assassin bugs often are found sitting on flowers lying in wait for other insects to visit. If another insect, such as a fly, caterpillar or leafhopper, comes into reach the assassin bug will capture it and feed on it. Assassin bugs are true bugs, which means their mouthparts are straw-like beaks that are usually tucked under their heads.

As it feeds and molts, the nymph becomes larger. This individual is almost an adult. You can tell by the size of the wing pads on the back of the thorax.

This is an adult assassin bug. Look how its color has changed, such as the legs have gone from spotted to solid green. Now its wings are red and cover the back of the abdomen. If you look really close, you may be able to see its beak curving under its head.

Look at those long antennae. That's one way it senses its food. It also uses its long front legs.

Assassin bugs like these are members of the genus Zelus. They are common throughout North America.

Have you ever seen an assassin bug like this?