Species that change type upon evolution:

Species that change type upon evolution:

Bug Egg Group:

1. Caterpie(Bug)->Kakuna->Butterfree(Bug/Flying)
2. Scyther(Bug)->Scizor(Bug/Steel)->Mega Scizor(Bug/Steel)
3. Pineco(Bug)->Forretress(Bug/Steel)
4. Wurmple(Bug)->Silcoon(Bug)->Beautifly(Bug/Flying)
5. Wurmple(Bug)->Cascoon(Bug)->Dustox(Bug/Poison)
6. Surskit(Bug/Water)->Masquerain(Bug/Flying)
7. Nincada(Bug/Ground)->Ninjask(Bug/Flying)/Shedinja(Bug/Ghost)
8. Trapinch (Ground)->Vibrava(Ground/Dragon)->Flygon(Ground/Dragon)
9. Burmy(Bug)->Wormadam(Bug/Grass)/Wormadam(Bug/Ground)/Wormadam(Bug/Steel)/Mothim(Bug/Flying)
10. Skorupi(Poison/Bug)->Drapion(Poison/Dark)
11. Karrablast(Bug)->Escavalier(Bug/Steel)
12. Scatterbug(Bug)->Spewpa(Bug)->Vivillon(Bug/Flying)
13. Grubbin(Bug)->Charjabug(Bug/Electric)->Vikavolt(Bug/Electric)
14. Blipbug (Bug)->Dottler (Bug/Psychic)->Orbeetle (Bug/Psychic)

Dragon Egg Group:

1. Charmander(Fire)->Charmeleon(Fire)->Charizard(Fire/Flying)
2. Horsea(Water)->Seadra(Water)->Kingdra(Water/Dragon)
3. Magikarp(Water)->Gyarados(Water/Flying)
4. Dratini(Dragon)->Dragonair(Dragon)->Dragonite(Dragon/Flying)
5. Swablu(Normal/Flying)->Altaria(Dragon/Flying)
6. Bagon(Dragon)->Shelgon(Dragon)->Salamence(Dragon/Flying)
7. Skrelp(Poison/Water)->Dragalge(Poison/Dragon)
8. Jangmo-o(Dragon)->Hakamo-o(Dragon/Fighting)->Kommo-o(Dragon/Fighting)

Fairy Egg Group:

1. Togepi(Fairy)->Togetic(Fairy/Flying)->Togekiss(Fairy/Flying)
2. Azurill(Normal/Fairy)->Marill(Water/Fairy)->Azumarill(Water/Fairy)
3. Shroomish(Grass)->Breloom(Grass/Fighting)
4. Snorunt(Ice)->Glalie(Ice)/Froslass(Ice/Ghost)
5. Hatenna (Psychic)->Hattrem (Psychic)->Hatterene (Psychic/Fairy)

Field Egg Group:

1. Nidoran Female(Poison)->Nidorina(Poison)->Nidoqueen(Poison/Ground)
2. Nidoran Male(Poison)->Nidorino(Poison)->Nidoking(Poison/Ground)
3. Seel(Water)->Dewgong(Water/Ice)
4. Eeveelutions
5. Torchic(Fire)->Combusken(Fire/Fighting)->Blaziken(Fire/Fighting)
6. Seedot(Grass)->Nuzleaf(Grass/Dark)->Shiftry(Grass/Dark)
7. Chimchar(Fire)->Monferno(Fire/Fighting)->Infernape(Fire/Fighting)
8. Piplup(Water)->Prinplup(Water)->Empoleon(Water/Steel)
9. Bidoof(Normal)->Bibarel(Normal/Water)
10. Riolu(Fighting)->Lucario(Fighting/Steel)
11. Tepig(Fire)->Pignite(Fire/Fighting)->Emboar(Fire/Fighting)
12. Drilbur(Ground)->Excadrill(Ground/Steel)
13. Chespin(Grass)->Quilladin(Grass)->Chesnaught(Grass/Fighting)
14. Fennekin(Fire)->Braixen(Fire)->Delphox(Fire/Psychic)
15. Bunnelby(Normal)->Diggersby(Normal/Ground)
16. Pancham(Fighting)->Pangoro(Fighting/Dark)
17. Litten(Fire)->Torracat(Fire)->Incineroar(Fire/Dark)
18. Popplio(Water)->Brionne(Water)->Primarina(Water/Fairy)
19. 
    

Flying Egg Group:

1. Fletchling(Normal/Flying)->Fletchinder(Fire/Flying)->Talonflame(Fire/Flying)
2. Rowlet(Grass/Flying)->Dartrix(Fire/Flying)->Decidueye(Grass/Ghost)
3. Rookidee (Flying)->Corvisquire (Flying)->Corviknight (Flying/Steel)

Grass Egg Group:

1. Oddish(Grass/Poison)->Gloom(Grass/Poison)->Vileplume(Grass/Poison)/Bellossom(Grass)
2. Cacnea(Grass)->Cacturne(Grass/Dark)
3. Turtwig(Grass)->Grotle(Grass)->Torterra(Grass/Ground)

Human-Like Egg Group:

1. 
   

Amorphous Egg Group:

1. Slugma(Fire)->Magcargo(Fire/Rock)
2. Ralts(Psychic/Fairy)->Kirlia(Psychic/Fairy)->Gardevoir(Psychic/Fairy)/Gallade(Psychic/Fighting)
3. Shellos(Water)->Gastrodon(Water/Ground)

Mineral Egg Group:

1. Onix(Rock/Ground)->Steelix(Steel/Ground)
2. Nosepass(Rock)->Probopass(Rock/Steel)
3. Rolycoly (Rock)->Carkol (Rock/Fire)->Coalossal (Rock/Fire)

Monster Egg Group:

1. Larvitar(Rock/Ground)->Pupitar(Rock/Ground)->Tyranitar(Rock/Dark)
2. Mudkip(Water)->Marshtomp(Water/Ground)->Swampert(Water/Ground)
3. Chewtle (Water)->Drednaw (Water/Rock)

Water 1 Egg Group:

1. Poliwag(Water)->Poliwhirl(Water)->Poliwrath(Water/Fighting)/Politoed(Water)
2. Corphish(Water)->Crawdaunt(Water/Dark)
3. Tympole(Water)->Palpitoad(Water/Ground)->Seismitoad(Water/Ground)
4. Froakie(Water)->Frogadier(Water)->Greninja(Water/Dark)

Water 2 Egg Group:

1. 
   

Water 3 Egg Group:

1. Shellder(Water)->Cloyster(Water/Ice)
2. Staryu(Water)->Starmie(Water/Psychic)
3. Crabrawler(Fighting)->Crabominable(Fighting/Ice)

Species that change type upon Mega Evolution:

1. Pinsir(Bug)->Mega Pinsir(Bug/Flying)
2. Charizard(Fire/Flying)->Mega Charizard X(Fire/Dragon)
3. Sceptile(Grass)->Mega Sceptile(Grass/Dragon)
4. Ampharos(Electric)->Mega Ampharos(Electric/Dragon)
5. Lopunny(Normal)->Mega Lopunny(Normal/Fighting)
6. Groudon(Ground)->Primal Groudon(Ground/Fire)

Species that change type upon evolution(Alolan Forms):

1. Pichu(Electric)->Pikachu(Electric)->Alolan Raichu(Electric/Psychic)
2. Alolan Vulpix(Ice)->Alolan Ninetales(Ice/Fairy)
3. Exeggcute(Grass/Psychic)->Alolan Exeggutor(Grass/Dragon)
4. Cubone(Ground)->Alolan Marowak(Fire/Ghost)

Species that change type upon evolution (Galarian Forms):

1. Galarian Ponyta (Psychic)->Galarian Rapidash (Psychic/Fairy)
2. Koffing (Poison)->Galarian Weezing (Poison/Fairy)
3. Mime Jr. (Psychic/Fairy)->Galarian Mr. Mime (Ice/Psychic)->Mr. Rime (Ice/Psychic)

Species that change type in other form changes.

1. Darmanitan(Fire)->Darmanitan Zen(Fire/Psychic)
2. Galarian Darmanitan (Ice)->Galarian Darmanitan Zen (Ice/Fire)
3. Hoopa(Psychic/Ghost)->Hoopa Unbound(Psychic/Dark)
4. Necrozma(Psychic)->Dawn Wings Necrozma(Psychic/Ghost)/Dusk Mane Necrozma(Psychic/Steel)->Ultra Necrozma(Psychic/Dragon)
5. Zacian (Fairy)->Zacian Crowned Sword (Fairy/Steel)
6. Zamazenta (Fighting)->Zamazenta Crowned Shield(Fighting/Steel)
7. Castform
8. Rotom
9. Meloetta
10. Oricorio

Multitype species:

1. Arceus
2. Silvally

Edit (31.12.2019): Added Sword and Shield changes.