These small bugs that are found crawling out of holes in Ukuku Prairie. They only appear on one screen, south of Kanalet Castle. They appear from a hole in the ground when Link gets close. They are very easy enemies to handle, and can be defeated with a single sword swipe. They will endlessly continue appearing from the hole until you leave this screen.
Oracle of Seasons and Oracle of Ages
In Oracle of Seasons, the mini-boss of Snake's Remains, Facade, will cause Beetles to fall from the ceiling, which damage Link if he touches one. One attack with a sword is enough to do away with them.
The Minish Cap
There are two different variants of Beetles found in The Minish Cap, including Black Beetle and the more uncommon Red Beetle. These pesky insects will attach themselves to Link, causing Link to be unable to use his sword, and slowing him down until Link shakes them off. They will not deal any actual damage to Link and can be defeated with a single sword slash. The Red Beetles will appear in the boss battle with Mazaal in the Fortress of Winds.