TOPIC: Burrowing flies?

I found little holes in loose fill cellulose insulation.
They looked like water had dripped there but there was not water.  No crusty cellulose that could indicate water that had dried up.
There were plenty of dead flies on top of the insulation.  Could they have caused these holes?  I will attach some photos but I don't know if they will be of much help.
Thanks.

Cellulose insulation is mixed with boric acid.  The acid does two things -  it kills insects so they will not eat it and it will not burn.  I think it is very good insulation.  It has more R-value per inch than fiberglass or foam and fills gaps better.

I agree that it is a good insulation but I wasn't aware of the insect killing properties.  Have you ever seen those little holes though?  Any ideas?

Maybe they laid eggs and that was their demise!