Analysis of Silence again

Silence again. The glorious symphony
Hath need of pause and interval of peace.
Some subtle signal bids all sweet sounds cease,
Save hum of insects' aimless industry.
Pathetic summer seeks by blazonry
Of color to conceal her swift decrease.
Weak subterfuge! Each mocking day doth fleece
A blossom, and lay bare her poverty.
Poor middle-aged summer! Vain this show!
Whole fields of Golden-Rod cannot offset
One meadow with a single violet;
And well the singing thrush and lily know,
Spite of all artifice which her regret
Can deck in splendid guise, their time to go!