Explanation of an Antique Gem

A YOUNG fig-tree its form lifts high
Within a beauteous garden;
And see, a goat is sitting by.
As if he were its warden.
But oh, Quirites, how one errs!

The tree is guarded badly;
For round the other side there whirrs
And hums a beetle madly.
The hero with his well-mail'd coat

Nibbles the branches tall so;
A mighty longing feels the goat
Gently to climb up also.
And so, my friends, ere long ye see

The tree all leafless standing;
It looks a type of misery,
Help of the gods demanding.
Then listen, ye ingenuous youth,

Who hold wise saws respected:
From he-goat and from beetles-tooth
A tree should be protected!