Beetle Colony

The beetles are minor antagonists in the first movie. One of them managed to clip Reese's tail with the horns eventually alerting their presence, forcing Reese and Fievel to run through the tunnels ahead.

They chase both Reese and Fievel through the sewers to eat them, but the duo loses them by going over a chasm.

Many of the black beetles fell into the sewer lake and drowned, some were eaten by what appeared to be a piranha, a sewer eel, or a Shark. However only one was left alive, and that Beetle was the very insect that chomped Reese's tail in the Tunnels, this very Beetle didn't let go of Reese's tail their by Slowing him down to the point that Fievel had to grab his hand and help him make it to the Sewer River chasm.

Though Fievel was able to make across the Chasm by swinging on a hanging Vine or rope, and making it to the other side before the rocks came down, Reese was unable to make it to the other side due to the weight of the weight of the Beetle that has his Tail in its horn jaws, leaving him to dangle against the Vine over the sewer river, while the rest of the Beetles are drowned and consumed by a Predator.

Although he was able to swing to the cliff and make it to the edge, the Weight of the Beetle began to pull him down towards the River below, where eventually realizing that the situation for him was hopeless, Reese ordered Fievel to get away, that only he will slow him down, and that it was it for him here.

Fievel however protests this by running away from the ledge, much to Reese's delight on thinking he was going to escape, but is horrified when Fievel returns with a large rock in his Paw, he manages to toss several rocks at the Beetle that was chomping Reese's tail, forcing the insect to at last let go, and be consumed by the Predator down below.

The entire Beetle Colony, that chased and attempted to eat both Reese and Fievel was than devoured alive after the last Beetle that had Reese's tail was both killed by drowning in the lake and being eaten by the Predator.

Trivia
Strangely, they are photo-realistic instead of cartoon in the movie, while Digit is a cartoon cockroach. Also the Scorpion which is also realistic but semi-cartoon (due to their snake-like eyes instead of arachnid-eyes).

Many fans are confused them are thought to be the Cockroach Colony (arguably, Digit is only cockroach character) because they are mostly spend in sewers also searching food scraps, while the Beetle Colony does not live in sewers instead they lived in somewhere in garden, parks, or even in forest.