Hi Karl,

It looks like the affected trees are mature, and could have been suffering from decline related stress as a result. 
Trees have life spans just like we do, and when they are older stressors like drought, root compaction, or cankers can cause additional issues to take place. 

One of the pairs of trees appears to have been suffering from a canker for some time as evidence by the scar tissue along the edges of the long vertical wound. Cankers can be caused by fungus or bacteria (in this case I suspect fungus) and the only treatment for canker is to cut out affected tissue. Not possible when the trunk is affected. 

I'm not sure the other two trees had a canker, but if the bark peeled back easily it could have (the black streaks may also be an indicator). 

Once trees are stressed for the aforementioned reasons, opportunistic insects readily attack the weakened tree. I suspect this is the case and that the insect is not the primary issue. Other, healthy trees can likely ward off the insect. 

To limit stress on the remaining trees you should avoid driving machinery (including lawnmowers) close to the base of the tree. This can compact the soil, and maples do not handle compacted soil well. This is especially true in sandy soils.  

It would also be a good idea to water the trees if no rain occurs in 4-5 days, especially during hot summer days. Best to do this in the evening; letting a hose run at the base of the tree for 30-40 minutes will give the tree a deep water. 

If you do cut these trees down, you may keep them for firewood, especially if the bark is easily removed. Removing the bark generally kills any pests within, and prevents the reproduction and spread of any remaining insects. 

I hope this helps. Please do feel free to reach out if you have any follow up questions. 

Thank you, 
Julie