Swamp Moth
Source: Pet Battle. Prefers to dwell in wet, muddy areas and feed on Sorrowmoss nectar. Flying type. I think it is pretty reasonable to assume that this pet, along with the Moccasin in Swamp of Sorrows shares a spawn with all other pet battle pets in this areas.
The Swamp Moth is a wild pet found in the Swamp of Sorrows in the Eastern Kingdoms, appearing most often as a secondary pet in battles rather than a standalone spawn.
Guide awaiting review
Clear Area Battle Pets
Fly the circuit bordered by Stonard, Splinterspear Junction, and the Harborage, battling every pet you encounter — particularly the abundant Toads, Huge Toads, and Water Snakes. Clearing out all pets in this area causes Swamp Moths to respawn within roughly 10 minutes.
Engage Secondary Spawns
Swamp Moths appear primarily as secondaries during land-based pet battles in the zone. Out of 20 tracked battles, Swamp Moths showed up 4 times, making them the least common secondary behind Frogs, Huge Toads, Water Snakes, and Parrots.
Check Known Solo Spawn Spots
Swamp Moths do occasionally spawn on their own but are very rare. One was found along the north eastern wall of Marshtide Watch at 71, 33, and another at the northern edge of the small pond at Purespring Caverns at 17, 60.
Tips
The vast majority of Swamp Moths found in the wild are Poor or Common quality, with Rare quality being extremely uncommon even after several hours of farming.