Can you please help identify these insects damaging the bark of my maple tree?

Question: Hello! We have a single young maple tree in our property that had been previously healthy. Earlier this spring, we noticed that some of the bark of the tree was splitting at the base of older branches. It is more noticeable in lower branches vs higher ones. After close inspection, we realized that very small insects were the cause of the damage described above. The foliage of the tree looks normal.   Are these some type of borers? This tree is isolated from other maple trees.   I am attaching some images of the branches and the insects. Thank you!

responder: An Ask Extension Expert Replied June 07, 2023, 5:04 PM EDT
response: Hello!   The tiny little critters underneath the bark are actually duff millipedes. They feed on fungi and decaying organic matter, and they are commonly found under the bark of trees. They are NOT the cause of damage in your tree, but rather they found the tree as an opportunity to find food. They won't harm your tree. More about duff millipedes here: https://webdoc.agsci.colostate.edu/bspm/ArthropodsOfInterest/DuffMillipede2018.pdf  Can you tell me more about your tree?Do you know what type of maple? When was it planted?Can you send photos of the entire tree in the landscape? Include a photo of the trunk base. How much water does the tree receive throughout the year? Any winter watering? Have you wrapped the tree for winter? Any products applied? (fertilizer, pesticides, etc.) The answers to your questions will help us determine what might be going, and what solutions might help the tree.  Let me know if you have any questions!   Thanks,  Lisa  Horticulture Specialist Colorado State University Extension, Arapahoe County

responder: The Question Asker Replied June 13, 2023, 4:31 AM EDT
response: Dear Lisa, Thank you so much for your response and the additional information on the millipedes! Below is what I know about the tree:Do you know what type of maple? No, I'm sorry, I do not know. It came with the house, which we own since 3 years ago.When was it planted?It was already tall when we purchased the house, we think it may be about 5 years old?Can you send photos of the entire tree in the landscape? Include a photo of the trunk base. Yes! Photos were taken last weekHow much water does the tree receive throughout the year? Any winter watering?The tree received water on a schedule from the lawn sprinklers during the summer. My husband waters the plants sometimes 2x day on very hot days. That includes the trees. We water plants and trees during the winter when it's above 30-40 degrees during the day. Have you wrapped the tree for winter? Yes, for the first two years we owned it with the paper sold for tree wrapping. I didn't wrap it last year.Any products applied? (fertilizer, pesticides, etc.)Only Revive once a year. I don't use pesticides in the surrounding lawn. Im not sure about my neighbors, though. Some of the surrounding plants have been fed with compost im previous years. Thank you so much!Ileana

responder: An Ask Extension Expert Replied July 21, 2023, 10:14 AM EDT
response: Thank you for reaching out.  I think the system did not reopen your question for Lisa.  You may contact her with follow up questions at <personal data hidden>.