When threatened they cluster together, generating electricity.
Hunter’s note
They usually drift about peacefully, but sometimes they cluster together and spit out a sharp, crackling flash that will stun and burn even large beasts like myself. Watch closely for an opening and move past them quickly.
Kills to complete
Inspect
Not counted by kills. Inspect it to complete the entry.
Game file
ZapBug · killsZapBug
Bestiary
170 Hunter's Journal entries, 37 marked as bosses
Data from build 22529139, updated
Overview
37 of the Journal's 170 entries are boss fights, and 36 turn up again in one of Hollow Knight's five Pantheons, the gauntlet fights Godmaster added. Grimm Troupe adds five more, tied to Grimm's traveling circus, and the Dream Nail unlocks 13 fights that don't exist anywhere else in the game. Only seven of those 13 are true Dream Warriors; the rest are White Defender, Grey Prince Zote with his Zotelings, and the Seal of Binding. Two entries skip the kill requirement completely and fill in as soon as you meet them: the Crawlid, which the Hunter finds beneath his notice, and your own Shade.
How the Journal Works
Kills to Complete
Kill counts to unlock an entry aren't a flat rule: most bosses and named encounters need just 1 kill, but common mobs like the Vengefly demand as many as 45 before the description and Hunter's note fill in.
Hunter’s Notes
The description under each entry is straight out of the Hunter's Journal and reads like a field guide. The italic note below it is the Hunter's own voice, usually funnier, sadder, or more pointed than the clinical entry above it: that's where most of Hollow Knight's incidental writing lives.