An S-shaped pattern formed when a stream flows through channels is called

meander

Explanation:

A meander is a series of regular sinuous curves in the channel of a stream/river/watercourse, thereby forming a rounded or "S"-shaped bend curve. Meanders are common in alluvial areas that have low gradients, where they are formed by the dynamics of the watercourse. The meander belt is the zone within which a meandering watercourse occupies on its floodplain. The sinuosity is a measure to calculate the degree of meandering in the channel of a watercourse.

emerald ash borer

the emerald ash borer is a green buprestid or jewel beetle native to north-eastern asia that feeds on ash species. females lay eggs in bark crevices on ash trees, and larvae feed underneath the bark of ash trees to emerge as adults in one to two years. hope this !