Swarms are daily occurrences in which a certain species of Pokemon is found, in a certain Route. The levels of a daily swarm can be between level 15-30 (15 levels range). You can find logs of the swarms at http://omegalegends.tk (which is the Pokémon Omega Legends website, accessible to anyone)
Some swarm Pokemon show up only when it swarms, so it would be beneficial to catch it as soon as possible. Others are maps, but the swarm makes it easier to get. These aren't called swarms, as they are not swarm exclusive. The swarm changes daily and any one may not show up for weeks or months, or could appear frequently. It is possible to meet a shiny form, which is then called a "Shiny Swarm". Shiny swarms are rarer than Shiny Map Pokémon, as they are not available at all times.
Most swarms only appear in their basic evolution. To obtain others, evolve a swarm you caught.
The Home Page and the Pokécenter list the swarm of the day, as well as the Route you can find it in. It will always be one of the Routes accessible to everyone, and not Route 529, or Iwanai Island, which are accessible only to users with 10,000 Trainerpoints and the ability to Dive.
- Mankey (evolves into Primeape starting at level 28)
- Doduo (evolves into Dodrio starting at level 31)
- Grimer (evolves into Muk starting at level 38)
- Porygon (evolves into Porygon-2 by trading and using the item Upgrade afterwards, evolves into Porygon-Z by trading and using the item Dubious Disk afterwards)
- Natu (evolves into Xatu starting at level 25)
- Wooper ( evolves into Quagsire starting at level 20)
- Snubbull (evolves into Granbull starting at level 23)
- Elekid (evolves into Electabuzz starting at level 30, evolves into Electrivire by trading and use the item Electrizer afterwards)
- Larvitar ( evolves into Pupitar starting at level 30, evolves into Tyranitar starting at level 55)
- Nosepass ( evolving into Probopass if you level Nosepass in Western Cavern Crater)
- Cacnea ( evolves into Cacturne starting at level 32)
- Wynaut ( evolves into Wobbuffet starting at level 15)
- Bagon ( evolves into Shelgon starting at level 30, evolves into Salamence starting at level 50)
- Beldum ( evolves into Metang starting at level 20, evolves into Metagross starting at level 45)
- Drifloon ( evolves into Drifblim starting at level 28)
- Glameow ( evolves into Purugly starting at level 38)
- Happiny (evolves into Chansey by using an Oval Stone, evolves into Blissey by happiness)
- Munchlax ( evolves into Snorlax by happiness)
- Skorupi ( evolves into Drapion starting at level 40)
- (possibly more to come)