What do the final two stanzas suggest about " a narrow fellow in the grass"?

Those two final stanzas suggest that although the poetess usually feels very comfortable being outdoors, she feels fear before the "narrow fellow in the grass". Her "tighter breathing" suggests that she is left breathless when confronted with this creature, breathless with fear or wonder, when it is close. She is frozen, cannot move due to the fact that she is very frightened.