John Keats' poem, "On the Grasshopper and Cricket," is a wonderful poem.
Keats, as a second-generation Romantic poet, pays special attention to nature in his poem, which is a characteristic of this kind of writing: the return to, and admiration for, nature.
Keats' first line tells use that "the poetry of earth is never dead." He states that it as a living thing, and, indeed, in his poem he proves just that: the creatures come alive to the reader.
First of all, Keats allows the reader to care for the grasshopper immediately, personifying him as a creature who after he has had his "fun" in the warm weather, he finds a weed to relax under while he makes his "summer song."
The contrast the reader is presented with (in the change of seasons) is artfully joined with the line:
The poetry of earth is ceasing never...
...as Keats repeats the sentiment with which he began the poem. Even after the summer ends, and humans retire inside, missing the lushness of trees, the "mowing of mead," and the sounds of birds and grasshoppers, the cricket continues the poetry of earth, in a way taking up the grasshopper's job.
The quiet of winter is disturbed, near the warmth of the stove, by the shrill "call" of the cricket, continuing nature's song:
...from the stove there shrills
The Cricket's song, in warmth increasing ever,
And seems to one in drowsiness half lost,
The Grasshopper's among some grassy hills.
In drowsiness, the grasshopper's call is echoed in the sounds of the cricket.
Our two contrasts are the seasons: summer and winter, and the song of grasshopper and cricket. And though the elements of these contrasts are very different in their extremes, the poetry of nature does not end with the season, but lives on, simply in a different form.