Thank you for the pictures, they are helpful.
Your best action is to get an on site diagnosis from a certified arborist this spring as the tree is leafing out. The insects you have could be the source of the problem or they could just be taking advantage of dying wood that can be caused by one of many other possibilities. Maple tree decline/dieback can be caused by a girdling root, root zone damage, too little water during a drought, or several other things.
Find a certified arborist at www.treesaregood.com
. You want a certified arborist because they have gone to school and been trained in diagnosis of insect and diseases of all woody plants.
A second alternative to identifying the insect itself is to submit samples and pictures to the MSU Diagnostic Lab. Insect ID is usually free. Go to their website and read the instructions for submitting samples. You can print out the submission form. Include as much info as you can such as what time of year the dropping twigs start, how long it has been happening, kind of maple you have. Include pictures of the whole tree during the growing season, if possible. If you have questions about their instructions you may call them during business hours. The lab website is ---
The pictures you provided could be the larvae of many different beetles that take advantage of dying wood. They could also be immature larvae of a twig pruner or a twig girdler insect. Until you have a diagnosis, keep twigs and other debris raked up, bag it and seal the bag. If larvae are in this debris you will help reduce the population by doing this.
Note that this time of year(winter) twigs are broken or chewed off by squirrels, too. We guess that they do this for a variety of reasons, and to a variety of trees. By examining the ends of the twigs, you can sometimes see that the twig is cut at an angle, as if with a hand pruner. Here is info about that---
Keeping your trees as healthy as possible, especially during droughts during the growing season, will help them the most. Here is an article that discusses that, should you like to read it.
Twig pruner and girdler information---
As you can see, more investigation is needed to determine what is the root cause of the problem. I hope this information helps you.