Menderbug

Hunter's Journal
'' Member of an elusive guild of bugs fixated on the maintenance of Hallownest's many signs and wayposts.  The bugs of Hallownest were obsessed with building things. What strange little minds they had.''

Behaviour
Menderbug has an extremely low chance to spawn at the entrance of Forgotten Crossroads right below DIrtmouth. To spawn, the following conditions must be met: Upon seeing the player, the Menderbug will flee and quickly leave the room.
 * The sign at the entrance must be destroyed
 * The player must leave and re-enter the room

Tactics
One of the easiest ways to catch him is in late game, after acquiring either Kingsoul and/or Salubra's Blessing to refill SOUL easily. Enter Forgotten Crossroads from Dirtmouth by using Desolate Dive. This will destroy the sign upon landing and, if he spawns, will also kill the Menderbug. He can also be spawned by leaving the room to the left or right within Forgotten Crossroads but that takes significantly more time and it's easier to miss the chance to kill him before he flees.