Kabutomushi

Beetles are insects that have made a few appearances throughout the Mario series.

Donkey Kong 3
Beetles make their first appearance as enemies in Donkey Kong 3. They appear in the 18th round and go down to the bottom of the screen, just like Buttiflies, and then charge across full speed, attempting to hit Stanley the Bugman.

The Super Mario Bros. Super Show!
Beetles appear in The Super Mario Bros. Super Show! episode "Princess, I Shrunk the Mario Brothers", where they have a rather minor role. A quartet of Beetles are shown to be living inside a drainpipe that a shrunken Mario and Luigi take refuge inside of. As the Beetles are hungry, they chase Mario and Luigi through the drainpipe in an attempt to eat them, although Mario and Luigi manage to escape. In this appearance, the four Beetles resemble The Beatles.

Super Mario RPG: Legend of the Seven Stars
In Super Mario RPG: Legend of the Seven Stars, Booster collects beetles, but does not catch them himself, instead forcing his Snifits to make a hobby of capturing the beetles for him. By renting a Beetle Box for 150 coins and traveling to Booster Hill, home of the Beetle Race minigame, anyone can join in the fun and try to catch beetles along with the Snifits. Each Beetle can then by traded at Beetles Are Us for a predetermined amount of coins. Golden Beetles are worth one Frog Coin, male Beetles are worth fifty coins, and females only one coin.

Earlier Mario enemies Buzzy Beetle and Battle Beetle can be considered beetles, but look vastly different than the generic Super Mario RPG: Legend of the Seven Stars beetles.