Hwurmp

"Tiny and placid but swells to enormous size when threatened. Extremely amusing creature."

Hwurmps are enemies in Hollow Knight. They are tiny creatures who have powerful, expandable lungs which allow them to swell up to an enormous size.

Behaviour and Tactics
Floats around passively until the Knight approaches it, after which it slowly floats towards them. Upon taking damage or colliding with another enemy or the Knight, it inflates and bounces off objects, walls and water surfaces. After a relatively short period, it reverts to its original form. If it inflates inside a tight space where its inflated body cannot fit, it instantly dies.

Be careful when dealing with them in bigger numbers as they inflate each other upon contact and groups of them can easily and quickly fill up a room.

Location
They are found mainly in the north part of the Royal Waterways. Some can also be seen in the lower part of Isma's Grove.

Trivia

 * The Hwurmp is one of the few enemies that respawns upon leaving and re-entering the room.
 * An early screenshot shows the Hwurmps in Isma's Grove with a green colour instead of pink.