Vermiculation

Vermiculation is a surface pattern of dense but irregular lines, so called from the Latin "vermiculus" meaning "little worm" because the shapes resemble worms, worm-casts, or worm tracks in mud or wet sand. The word may be used in a number of contexts for patterns that have little in common. The adjective vermiculated is more often used than the noun.
Vermiculation naturally occurs in patterns on a wide variety of species, for example in the feathers of certain birds, for which it may provide either camouflage or decoration. Several species are named after this trait, either in English or by the Latin vermicularis. 
It also appears in architecture as a form of rustication where the stone is cut with a pattern of wandering lines. In metalwork, vermiculation is used to form a type of background found in Romanesque enamels, especially on chasse reliquary caskets. In this case the term is used for what is in fact a dense pattern of regular ornament using plant forms and tendrils. In Ancient Roman mosaics Opus vermiculatum was the most detailed technique, and pieces are often described as "vermiculated" in English.
Species named "vermicularis".
Some species have patterns that look like little worms, others actually are little worms. Some of these names have now been superseded.
Other uses.
The rock texture myrmekite is composed of vermicular "worm–like" intergrowths of quartz and feldspar.