Denimopedia – Honeycombs
The denim on the back of the knee gets creases from the repeated folding. It creates a unique fading that will appear in a pattern that looks similar to the honeycombs made by bees. You usually see these honeycombs on dry denim after a few weeks wearing.
When you finally wash your dry jeans, after at least six months, the honeycombs will be more visible.
The honeycombs tend to appear brighter on tighter fits while looser fits have wider fades. The cottons fiber breaks easier when the denim is heavier and more rigid than light-weight denim with stretch. Imagine folding cardboard and normal paper.