mosquito, gnat
蟁 centers on small flying insects that bite or annoy: a mosquito or gnat.
蟁 combines 民 (people) with 䖵 (two insects), likely suggesting insects that bother people. The exact historical development is uncertain.
The top 民 (people) is bothered by the bottom 䖵 (two insects): imagine a swarm of mosquitoes and gnats pestering a crowd.
For ブン, picture a mosquito buzzing near your ear with a deep 'bun' sound: bun -> ブン, and the insect annoys the people below.