European Sawfly
Neodiprion sertifer
Notes:

One year the bluebirds did not nest in the yard. The sawflies look back on that as a good year. They covered almost every branch of the red pine.

Normally though, they don't do much damage. I suspect the bluebirds and phoebes have something to do with that.

Photos:
Don't blow it - good planets are hard to find.
Quoted in Time