Parasprites

Parasprites are cute locust-like creatures from the Everfree Forest. While they may look cute, they have been discovered to have ravenous appetites, eating anything in sight many times their size. They are able to reproduce by coughing or hacking newborn parasprites every few minutes after consumption. Because of this, a large swarm left unchecked could easily devour large crop fields in a matter of seconds.

In Swarm of the Century, Fluttershy found one and brought it over to show her friends. However, the creatures began multiplying and soon became more trouble than they were worth in Ponyville. Because of their mysterious background, she, Twilight Sparkle, and Zecora did not have any information on how to deal with them. Fluttershy tried to communicate with them but to no avail. Twilight magically controlled their appetite, only to have them switch from food to practically everything else. Zecora recognized them when Twilight brought one to her, but she only concluded that Ponyville wouldn't last long due to the insects' eating habits.

Pinkie Pie was the only one known to have had some experience with them in the past, and discovered that they were attracted to music. This discovery inspired her to act as a one-pony band, using random musical instruments, to lead the entire swarm back to the forest before they completely destroyed the town.

Triva

 * Unlike most creatures encountered in the series, parasprites (and Diamond Dogs) have no parallel in classical mythology.
 * Parasprites are reminiscent of tribbles from Star Trek, however, and may draw their origins from there.
 * Pinkie Pie and Zecora are the only characters shown to actually know what Parasprites are.