Been bugging me for years

Observation - Been bugging me for years. Description: Going back some years ago, I ran into an insect that I had never seen before. My curiosity has been bugging me for years wondering what it was. The insect shell is approximately 1 cm long, 0.5 cm wide, and maybe 1 to 1.5 mm deep. The shell is oval

Going back some years ago, I ran into an insect that I had never seen before. My curiosity has been bugging me for years wondering what it was.

The insect shell is approximately 1 cm long, 0.5 cm wide, and maybe 1 to 1.5 mm deep. The shell is oval shaped with one point flattened with a tiny opening. The color is a mottled grey color, almost like it was made of grey sand. Something that looks like it would blend in with a tree trunk.

After dissecting the shell with a razor, I butterflied the shell. Inside the shell appeared to be a silken construction and inside was a tiny worm-like insect approximately 1.5 mm long that was white with a red head.

It appears that the shell is a protective home for the insect and the insect moved by darting its head through the hole in the shell to drag the shell with it as it moved.

Hopefully someone will be able to tell me what I saw.