Answer:
What is long and slim, works in light. Has but one eye, and an awful bite?
The more of them you take, the more you leave behind. What are they?
Different lights do make me strange, thus into different sizes I will change.
We are all around, yet to us you are half blind. Sunlight makes us invisible, and difficult to find.
I move without wings, Between silken string, I leave as you find, My substance behind.
Break me and I am better immediately set and harder to be broken again.