In the beginning of the poem 'lethargy' lies 'here and there in coils'. This portrays the snakes as languid, peaceful creatures. They are sleeping in the 'white-hot midday' sun. However, the Ringsnake is then said to be pouring 'slowly through an opening like smoke'. Using smoke as a simile is effective in changing the tone of the poem.
Smoke moves very ominously, and the snakes are now waking from their peaceful sleep and emerging.
Toward the end of the poem, the tone changes again. This shows that the humans see the snakes as cunning predators. This snake is in camouflage, and ready to attack any victim who is not aware of the danger. The use of imagery in this poem describes the manner of the snakes when placed in different situations. Plath uses symbolism to describe the relationship between man and snake.