Wisps at mating season.
This is not offical WoW Freedom lore, and should not be taken for anything exept a good laugh.[]
"The mating ritual starts with 2 wisps of opposite genders gathering wood in trees near eachother. Slowly, they move on to the same tree. After gathering exactly 300 wood, the wisps start.. err.. mating. The female wisp swallows the male wisp which clones himself; then the female wisp, after gathering 955 wood, gives birth to two, young wisp males. Once the process is done, the female wisp goes to gather more wood, but on another tree. For producing female wisps, you need 2 female wisps and 1 male wisp.
The procedure is done by one of the females swallowing the male, and the other female swallowing the female who swallowed the male. Then, the female absorbs the male's cloning power and clones herself, losing the cloning ability. Then, two young, healthy wisp females are born; they then separate, looking for other trees to gather."