Most Bug Pokémon grow quickly to evolve sooner than other types. This makes them very weak as a result and were almost useless in Generation 1, but have improved since then. Bug moves are super-effective against Grass, Psychic, and Dark Pokémon, but are not very effective against Fire, Fighting, Poison, Flying, Ghost, and Steel Pokémon. Grass, Fighting, and Ground Pokémon are not very effective against Bug Pokémon, but Fire, Flying, and Rock Pokémon are super-effective against them. There are 90 Pokemon in this category.
Here is a list of some bug types:
Caterpie is a caterpillar looking Pokémon that is often hunted by other bird Pokémon. They have antennae on the top of their heads that will emit a terrible stench if the Caterpie is frightened to protect it from predators. It can also spit a string to entangle foes. They have to constantly eat in order to meet their energy requirements to evolve into Metapod, which shortly thereafter evolves into Butterfree. Butterfree Pokémon can create dusts from their wings that can be toxic, paralyzing, or induce sleep on their predators. The favorite flower of this Pokémon is the Vermilion flower.
Wurmple has a branched evolution which means it has more than 1 pokemon it could evolve into depending on its personality type. As they are targeted prey for Swellow and Starly Pokémon they desperately try to evolve quickly and release poison from the spikes at their rear end to defend themselves. If Wurmple evolves into Cascoon then it will become a Dustox. If a Wurmple evolves into Silcoon, it will become a Beautifly. If it evolves into the butterfly resembling Beautifly Pokémon, they will be able to sap energy from other attackers to restore their own health and gets very aggressive if disturbed while sipping nectar. If it evolves into the moth-like Dustox Pokémon it will be a nocturnal Pokémon that is attracted to bright lights. If attacked while as a Cascoon, a Dustox will always remember the face of the attacker and will seek revenge upon evolution.
Kricketot and Kricketune are both very musical Pokémon. Kricketots can create a xylophonic sound by shaking their head and rubbing their antennae together, which is how they communicate. They usually live in trees and cannot be found during the mid-day and afternoon. Kricketune can make all types of music by rubbing their arms together (probably why they're called Kricketune). They can also use their now scythelike foreparts for a lot of new attacks. Its emotions are signaled by the type of melody it creates. There is a village that hosts a contest based on the amazingly variable cries of the Kricketune.
Now, some known Bug type trainers are:
Burge
Castelia City Gym Leader
Unova
Aaron
Elite Four
Sinnoh
Bugsy
Azalea Town Gym Leader
Johto
This type is only super-effective against Grass and Fairy, but overall is one of the more under-developed types in Pokémon. It does a little better defensively than offensively, but the biggest advantage for Pokémon of this type is through status moves like Toxic. Poison moves are not very effective against Poison, Ground, Rock, and Ghost types, and have no effect on Steel types. Grass, Fighting, Poison, and Bug types are not very effective against Poison types, but Ground and Psychic Pokémon are very effective against them. There are 69 different Poison types and some of them are listed below:
This family of Pokémon can sense danger and vibrations with their tongue and they have the ability to swim, with Arbok being able to go underwater for long periods of time. Ekans do not have the ability to add venom to its bite until Arbok when it has a terribly poisonous bite. Ekan's favorite food is a Pidgey or Spearow egg from their nests. Arbok hunt smaller Pokémon and have the ability to regrow parts of their body if it has been chopped off.
Nidoran is split into a female and male version of the Pokémon, making them very unique. The female version of the Pokémon is a blue color and evolves into Nidorina and then Nidoqueen, and is overall more docile and protective than the male version. All versions of this Pokémon are able to eat poisonous fruit and plants while being uneffected by them. The male version of Nidoran is a more purple color and evolves into Nidorino and then Nidoking. The male version of this Pokémon is far more vicious and can cause very large tremors by slamming on the ground. They use their powerful tail to thrash and crush the bones of their prey. Female versions are found in expansive hot savannas and plains, while male versions are found in grasslands, rough terrains, and forests.
Gulpin can swallow anything its own size since they are made of practically all stomach. Swalot can swallow something as large as a car tire, and the only thing their stomach acid cannot dissolve is the lining of its own stomach. Their stomach acids can melt scrap iron and they eat in large quantities since they can handle anything. They both often live in grassy plains, but occassionally a Gulpin can migrate into cities and will eat anything in sight no matter what the damage. Swalots are generally carnivorous and will swallow their Pokémon prey whole after dousing it with poison from its pores.
Some known poison type trainers are:
Janine
Fuchsia City Gym Leader
Kanto
Koga
Elite Four (used to be the Fuchsia City Gym Leader)
Kanto
Roxie
Virbank City Gym Leader
Unova