To compete, Trainers must catch the single best Bug-typePokémon they can find. To do this, Trainers are given twenty Sport Balls (similar to Safari Balls; called "Park Balls" in Generation II), and they are only allowed to use a single Pokémon from their party. The rest of a Trainer's Pokémon and all of their items remain with the contest officials until the competition is over.
Any Pokémon caught will be recorded in the Pokédex, but only one Pokémon can be kept to be judged. The Pokémon that is judged may be kept after the competition.
The competition ends when all the Sport Balls are used, the Trainer blacks out, the Trainer leaves the park, the Trainer chooses to quit the competition from the menu, or 20 minutes have passed. After that, the judging will occur, in which Trainers are scored on their skills of capturing rare and powerful Pokémon.
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
Scyther, Pinsir, and one family of Bug-type Pokémon (Caterpie, Metapod and Butterfree in Silver, Weedle, Kakuna and Beedrill in Gold) can only be caught during the Bug-Catching Contest. All the others can be caught in the wild outside the contest.
16 points if half of the Defense IV (rounded down) results in an odd number, 0 otherwise
8 points if half of the Attack IV (rounded down) is odd, 0 otherwise
4 points if half of the Special IV (rounded down) is odd, 0 otherwise
1 point if half of the Speed IV (rounded down) is odd, 0 otherwise
1/8 of the current HP of the Pokémon, rounded down
1 point if the Pokémon is holding an item, 0 otherwise
The score earned for a given Pokémon in Generation IV is the sum of the following:
The level of the Pokémon relative to the maximum that can be found in the contest (e.g. before the National Pokédex, the maximum value for Paras would be 17, but after the National Pokédex, this would be 34), as a percentage
The Pokémon's IVs relative to the maximum (186), as a percentage
The Pokémon's HP relative to its maximum, as a percentage
In the Generation II games, each NPC contestant has three possible base scores. Five of the ten NPCs are randomly chosen to appear in the contest, and each of them randomly receives one of their three base scores, plus a random bonus of up to 7 points.
In The Bug Stops Here, Ash and Casey competed in the Bug-Catching Contest. During the competition, Casey caught a Weedle, and her Chikorita evolved into a Bayleef. Ash won the competition with a Beedrill, earning himself a Sun Stone. After the competition, he gave the Beedrill to Casey, being aware of her love for Pokémon with yellow and black stripes.
In the anime, the Contest can be followed from a giant screen outside of the park. It also has several other notable differences from the games.
Only the winner is allowed to keep the Pokémon they caught.
No consolation prize is available, neither are there any sort of rewards for anybody other than the champion, whereas such prizes can be earned in the games.
The contest implements strict age-limits: only children under 16 are allowed to participate.
The music used during the contest is a remix of the Kanto-based games' Bicycle music.
After the player obtains the National Pokédex and enters the contest on Thursdays and Saturdays, some of the other competitors may be announced as having caught a Pokémon in the Caterpie or Weedle lines, despite those Pokémon not being available to the player on those days.
In Generation IV, if at the end of the contest the player has a full party and their newly captured Pokémon is sent to the PC, it is referred to as "Bill's PC" (instead of "Someone's PC") even if the player has not yet met Bill.