'Adders have faces intense with hatred; hot with it...'

What had caught my eye in the heather was the zigzag, a pattern too clear to look natural. The shadows cast by bracken leaves have similar shapes. In these shadows, the zigzag evolved, presumably, but somehow the scatter of light and shade on the forest floor became on the snake a regular wavy line. It breaks up the animal’s outline. Hawks and crows see the snake from above. People do too. When the snake moves, winding through stalks and shadows, the zigzag goes in different directions, confusing the eye. On a motionless snake, it is insolently clear. In the heath’s debris, the zigzag looks stylized, like a printed or ceramic pattern, a logo or uniform, a badge of power and purpose.

-- from Our Adder by Richard Kerridge