Before the National Park (Route 35), there is a path through the grass you can take to find TM 04, Rollout.
On Tuesdays, Thursdays, and Saturdays, the National Park holds a Bug Catching Tournament. To enter you have to talk with one of the guys standing by the doors of either entrance. You can only take one Pokémon with you to battle the wild Bug Pokémon, the rest will be held for you until the contest is over Try And Make Sure it knows something like Hypnosis or Thunder Wave or something else that assures it to not be able to move. The contest is free, and you'll get 20 Park Balls to capture the Pokémon.
Whenever you catch more than one Pokémon in this contest, you'll be asked whether you want to switch it with the first one you caught. If not, your Pokédex will still record that you caught that Pokémon, you just won't get to keep it. You only get to keep one Pokémon from the contest, so all others will mysteriously disappear. The 1st place winner gets the Sun Stone.

Pokémon Seen Whilst In The Game
Caterpie	Metapod	Butterfree	Weedle	Kakuna	Beedrill
Common	Uncommon	Rare	Common	Uncommon	Rare
Paras	Venonat	Scyther	Pinsir
Uncommon	Uncommon	Rare	Rare

Pokémon Seen Normally
Caterpie	Metapod	Pidgey	Sunkern	Hoothoot
Morn/Day: Common	Morn/Day: Common	Morn/Day: Uncommon	Day: Uncommon	Night: Always

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