Larvadar starts off as purely a Bug-type Pokémon, but eventually becomes a Bug- and Psychic-type when it enters its second and final evolution Pokémon Sword and Shield. It only remains to wait for level 10 for its second evolution, but then it becomes Astronelle at level 30.
You can find Larvadar in several places in the Galar region. You may have first found it in the Weald Slumberwing when you need to rescue the lost Moumouton. You might find him wandering around the land world of Cape The Giants in normal weather and in the Route 2 high level area.
After that you need to have a bit more luck on your end as you can still find Larvadar on routes 2 and 1, but he appears as an exclamation mark. You have to rush there to find out what a Pokemon is, so you can find something you don't want to encounter. You will have to do this several times. If you stick to Route 2, you will eventually come across one.
Larvadar, Coledome, and Astronelle evolutions also have spawns.
For Coleodome:
- Giant's Cap during all underworld weather conditions
- Route 5 in all weather, not in the outside world
- Stony Wilderness during thick fog, not in the outside world
- Giant's Mirror in normal weather, overcast, rainy and sandstorm, not in the outside world
- Giant's Cap in any weather, not in the outside world. You have the best chance of finding it in normal foggy, overcast, and cloudy conditions.
For Astronelle:
- Weald asleep in the all-weather high-level area in the outside world
- Lake of Outrage in normal weather, not in the outside world
You don't have the best chance of encountering Larvadar evolutions. Coleodôme's Giant's Cap spawn is pretty decent, so if you can't find a Larvadar ahead of time, you might want to grab it and breed it to acquire it to acquire Larvadar for your Pokédex.
Larvadar has a two-star Max Raid hideout you can find in the Wild Area, but you might have better luck with the Pokemon's traditional spawns.