Although Pixies appear to "fly", they are only capable of hovering about four tiles above the ground at most, limiting them to a similar horizontal "jumping" range as a Zombie. However, Pixies can also "climb" vertical walls in order to reach the player, limiting the effectiveness of pit traps.
Pixies' movement patterns complicate farming, as they float above shallow pools of lava and their bobbing movement makes it difficult to hit them with stationary traps. Minions with close-range attacks, such as Spiders, Ravens and Deadly Spheres, can mitigate this difficulty.
↑Information taken from the Desktop220.127.116.11 source code, method RegisterStatusImmunityItems() in Terraria.GameContent.ItemDropRules.ItemDropDatabase.cs. There may be inaccuracies, as the current Desktop version is 18.104.22.168.