The theme of Robert Frost's "Fireflies in the Garden" (1928) is based on a contrast between the 'genuine' and the 'imitation.' The 'genuine' is symbolised by the "real stars" in the sky and the 'imitation' is symbolised by the tiny "fireflies." It's dusk and the "real stars" have begun to shine in the sky above, at the same time, on the earth below, the fireflies with brightly lit up tails begin flitting about. Frost feels inspired to make a connection between these two seemingly unrelated phenomena.
"Emulate," could be used in a positive or in a negative sense.
If positive, Frost seems to approve of the effort of the minuscule fireflies in trying to imitate the stars above. To begin with they shine brightly but being tiny they die out soon and are no match for the heavenly stars which burn brghtly forever, however their attempt to shine like the stars is praiseworthy.
If negative, Frost seems to disapprove of the effort of the fireflies in trying to imitate the bright stars above in the sky. The implication is that the tiny fireflies are arrogant in trying to compete with the "real stars."
Human civilisation progresses by imitation. Role models help us to channelise our energies to achieve success. But there is a flip side to imitation-without being aware of our limitations we, like the tiny fireflies, are not able to "sustain the part" and often end up as pathetic failures.