Rockruff is an adorable Rock-type Pokemon introduced during Pokemon GO's Welcome to Alola event. It has a werewolf-styled evolution tree.
Rockruff can currently be found in Pokemon GO's raids and its egg hatches. Once trainers have accrued 50 candies, they can feed them to Rockruff and initiate its evolution into Lycanroc.
However, Lycanroc has two distinct forms: the Midday Form and the Midnight Form. A Dusk Form also exists, but it doesn't appear to have been implemented in the game yet.
These two forms differ in appearance and stats. They also require different evolution conditions.
Specifically, trainers who want Midday Lycanroc should evolve their Rockruff during the day. Meanwhile, those who want Midnight Lycanroc should evolve their Rockruff at night.
Differences between Lycanroc forms in Pokemon GO
Currently, Pokemon GO has very little data on the newest Alolan Pokemon, but some early comparisons can still be made.
According to Pokemon GO Hub, Lycanroc's Midnight Form has different learnable moves. Early measurements also seem to point to Midnight Lycanroc having higher maximum defense and stamina stats. However, this is yet to be confirmed as Lycanroc is still an incredibly new Pokemon in the mobile title.
Midday Form Lycanroc is capable of learning Sucker Punch and Rock Throw as Fast Moves. For Charge Moves, it can learn Stone Edge, Drill Run, and Crunch.
In contrast, Midnight Lycanroc can learn Counter and Rock Throw as Fast Moves, with Stone Edge, Psychic Fangs, and Crunch being its learnable Charge Moves.
This means Midnight Lycanroc has a focus on Fighting and Psychic-type moves to complement its Rock-type moves.
If Pokemon GO trainers are concerned about type advantages with the different forms of Lycanroc, there's nothing to worry about. Both Midnight and Midday versions of Lycanroc are mono Rock-type Pokemon, which means they should be kept away from Fighting, Grass, Ground, Water, and Steel-type moves/Pokemon.
As a Rock-type Pokemon, Lycanroc will receive Same Type Attack Bonuses (STAB) to its damage if it utilizes Rock-type moves. These moves work super effectively against Bug, Flying, Fire, and Ice-type Pokemon.
However, it isn't wise for trainers to only focus on a Rock-type moveset, as that will limit Lycanroc's type coverage in battle.
Picking up a Psychic or Dark-type move like Psychic Fangs or Crunch as a secondary Charge Move will help Midnight Lycanroc defeat a wider variety of Pokemon in type matchups.