Caterpie
Geography
Caterpie can commonly be found in the regions of Kanto and Johto in the Pokemon world. Caterpie is renowned as a bug type Pokemon that can be found among trees in forest such as the Viridian forest. Trainers can also order their Pokemon to bash trees in the Ilex Forest in order to encounter a Caterpie. Furthermore, Caterpie can be found during bug catching contests in the Johto region. If Caterpie were real on Earth, I'd assume that Caterpie could be found in temperate deciduous forests. Temperate deciduous forests would provide deciduous trees, as well as sufficient amounts of food for growth. Temperate deciduous forests can be found along the eastern coast of the U.S, parts of Europe and the eastern side of Asia. One reason temperate deciduous forests would be a great place for Caterpie's to live on would be that deciduous forests recover from disturbances much quicker than other kinds of biomes.
Diet
Caterpie resemble caterpillars, so we can already assume that, if Caterpie lived on Earth than it would eat leaves off of trees on temperate deciduous forests or other kinds of forests.
Behavior
Caterpie tend to eat a lot at their first stages of development. If Caterpie's were found on Earth, you’d most likely find them eating leaves endlessly throughout the day. Caterpillars on Earth grow hurriedly which is a normal part of their life cycle in order for them to turn into butterflies; this would also apply to Caterpies. A variety of caterpillars have special defense mechanisms that allow for protection against other creatures, in this case, Caterpie also have a special defense mechanism, which can be located on their antennae which wards off Pokemon because of a very putrid smell.
Metapod
Geography
Metapod can commonly be found in the exact same areas that Caterpie can be found in; Forests. If Metapod were real on Earth, I'd assume that Metapod would be found stagnant on trees.
Diet
Metapods do not eat anything at this stage of development.
Behavior
Metapod only use harden as a defense mechanism. If Metapod were found on Earth, they'd mostly be found immobile.
Butterfree
Geography
Buttefree can commonly be found on Kanto and Johto in the Pokemon world. Butterfree is also renowned as a "trophy" in the bug catching contests in the Johto region which indicates that it's a rare catch. If Buttefree were to be found on Earth, we would most likely see them in the same areas as Caterpie and Metapod; Temperate deciduous forests. I'd also assume that Buttefree can also be found migrating which relates to how Monarch butterflies migrate.
Diet
Butterflies on Earth collect pollen. I’d assume that if Butterfree were real on Earth, they'd most likely collect pollen, and feed on sugars off of rotten fruits.
Behavior
I’d assume that Butterfree would collect pollen on a daily basis, as well as migrate during times of frost.
Credits
Image credit goes to PokemonElite2000; The ultimate source for finding Pokemon sprites and Sugimori Artwork.
