Answer:
I am an insect and the first part of my name is the name of another insect. What am I?
I am a kind of coat that can only be put on when wet.
Crooked as a rainbow and slick as a plate ten thousand horses can't pull me straight.
Deep, deep, do they go. Spreading out as they go. Never needing any air. They are sometimes as fine as hair.
You write on me and secrets I can keep. In places never seen. I spin like a top. Though stiff as a board I'm often described like a mop.
I flow from the Homerβs mouth when he sees doughnuts.