Instructions
Travel to Route 35 and speak with Arnie. He will agree to give you a phone call the next time the Yanmas swarm.
Wait for Arnie's call. When you answer, he will tell you where to travel to meet the swarm of Yanmas. Follow Arnie's travel directions.
Use a technique, such as Hypnosis or Sleep Powder, to put a Yanma to sleep when you encounter the swarm. Continue your assault using weak physical attacks.
Throw a Poke Ball at the Yanma you have put to sleep when its health reaches one-third. Throw another Poke Ball if the first one misses. If the second one misses and it runs away, engage one of the other Yanma quickly before the swarm disperses.