There, Robert, you have kill'd that fly — ,
And should you thousand ages try
The life you've taken to supply,
You could not do it.
You surely must have been devoid
Of thought and sense, to have destroy'd
A thing which no way you annoy'd —
You'll one day rue it.
Twas but a fly perhaps you'll say,
That's born in April, dies in May;
That does but just learn to display
His wings one minute,
And in the next is vanish'd quite.
A bird devours it in his flight —
Or come a cold blast in the night,
There's no breath in it.

The bird but seeks his proper food —
And Providence, whose power endu'd
That fly with life, when it thinks good,
May justly take it.
But you have no excuses for't —
A life by Nature made so short,
Less reason is that you for sport
The fly is allowed to die by natural causes such as a “bird” or a “cold blast in the night”  because at that moment the fly is thinking good and is not frightened. 

Thoughtless Cruelty