Generation III Ability

Swarm

Strengthens Bug moves to inflict 1.5× damage at 1/3 max HP or less.

Swarm Effect

When this Pokémon has 1/3 or less of its HP remaining, its Bug-type moves inflict 1.5× as much regular damage. Overworld: If the lead Pokémon has this ability, the wild encounter rate is increased.

“Powers up Bug-type moves when the Pokémon's HP is low.”

Swarm Data

Introduced
Generation III
Pokémon
31
In short
Strengthens Bug moves to inflict 1.5× damage at 1/3 max HP or less.

Pokémon With Swarm

31 Pokémon can have Swarm.

Swarm Questions & Answers

What does Swarm do?
When this Pokémon has 1/3 or less of its HP remaining, its Bug-type moves inflict 1.5× as much regular damage. Overworld: If the lead Pokémon has this ability, the wild encounter rate is increased.
How many Pokémon have Swarm?
31 Pokémon can have Swarm.
What Pokémon have Swarm?
Beedrill, Scyther, Ledyba, Ledian, and Spinarak, and 26 more Pokémon can have Swarm — the full list is above.
When was Swarm introduced?
Swarm was introduced in Generation III.